The Eurypterida of New York/Volume 1/Appendix
Remarks on Beltina danai Walcott
1899. Beltina danai Walcott. Geol. Soc. Am. Bul. 10: 238, pl. 25, 26; pl. 27, fig. 2-6
Ever since the publication of the work cited, these fossils, referred to the Merostomata, have aroused great interest among geologists and paleontologists, principally for the reason that they come from beds considered by Mr Walcott as Precambric (Greyson shales of the Belt terrane in Montana). Merostomata from beds so ancient would be of especial interest to the phylogeny not only of the eurypterids but also of all related subclasses, since it might be postulated that forms of such age were the common ancestors of the Merostomata and Arachnida, and perhaps also of the Crustacea.
Through the liberality of the secretary of the Smithsonian Institution the authors have been able to investigate the principal types and a number of other selected specimens of Beltina. These specimens are in a dark fine grained somewhat micaceous shale which does not, in hand specimens at least, afford much evidence of shearing or distortion. The "Beltina" bodies lying parallel with the bedding of the rock are, it appears from the records, very abundant as the collections of the National Museum contain hundreds of specimens. They are flat films or smooth patches left by organic films, and these only in the rare instances which have been illustrated present suggestions of resemblance to known merostome organs. The fact of their very great age and their presumable primitive form as the possible ancestor of quite diverse classes of organisms should not too rigidly force our expectations of exact resemblance but in such a multitude of fragments the occasional approach to the outline of an eurypterid limb, as for example to the free ramus of a Pterygotus chelicera [op. cit. pl. 25, fig. 13] must be looked upon as favorable evidence, if supported by collateral facts, even though such a structure is vastly progressed over what we might deductively expect in these ancient organisms. Speaking broadly however the outlines of all these bodies that we have examined, are indeterminate; we can not avoid the conviction that such resemblances as have been indicated to eurypterid parts are casual and the illustrated specimens represent only a very slender percentage of the total specimens gathered. Aside from these imperfections of outline there should be, so far as experience goes, a crucial test in the matter of integumental sculpture, for everywhere among the fossil merostomes this structure is a guide and index even in inconsiderable fragments. There is no reason to assume the absence of this sculpture even in archaic or ancestral forms of the group, but in all the specimens of Beltina we have scrutinized there is no trace of it; nor is there of body segmentation or arm joints. Many of the Beltina bodies are bandlike fragments or patches which indicate an infolding or overlapping as though they had been floated into the muds as very thin and tenuous films rather than as the rigid parts of an arthropod test. We entertain no doubt that these bodies, or the greater part, are of organic origin and while unable, after careful study, to convince ourselves that they are merostomatous, yet to renewed efforts in the field they do give promise of a recognizable fauna.
Note on Proscorpius osborni Whitfield
Palaeophonus osborni Whitfield. 1885. Science, 6: 87, 88, fig.
Proscorpius osborni Whitfield. 1885. Amer. Mus. Nat. Hist. Bul. 1: 187, pl. 20
Proscorpius osborni Scudder. 1885. Zittel's Handbuch der Palaeontologie, 1 Abth., 2 Bd., p. 739, fig. 915a.
Proscorpius osborni Thorell. 1886. American Naturalist, 20: 269
Proscorpius osborni Whitfield. 1886. Science, 7: 216
Proscorpius osborni Scudder. 1886. U.S. Geol. Surv. Bul. 31: 28
Proscorpius osborni Laurie. Royal Soc. Edinburgh Trans. 1899. 39:557, pl. 3
Proscorpius osborni Pocock. 1901. Quart. Jour. Micr. Sci., ser. 2, 44: 309
Proscorpius osborni Fritsch. Palaeozoische Arachniden, 1904. p. 65, 78, fig. 81
Proscorpius osborni Fritsch. Miscel. Pal. I. Palaeozoica, 1907, p. 6, pl. 3
In addition to its eurypterids the Bertie waterlime of New York has furnished a specimen of a scorpion which represents one of the four species of Siluric scorpions now known. As it is not only associated with the eurypterid fauna, but also related to it structurally, we have thought it well to include the following note on this unique fossil, especially as it has been the object of much debate.
This scorpion was discovered in 1882 by Mr A. O. Osborn in the waterlime of Waterville, Oneida co., N. Y. Although found before the three European species, the discovery was not announced until 1885, shortly after the news of the discoveries of the Swedish and Scottish Siluric scorpions had aroused the interest of paleontologists. Professor Whitfield, to whom the specimen had been sent by Mr Osborn, first gave a brief description and figure of it in Science and in the same year produced a more elaborate description with figures in the Bulletin of the American Museum of Natural History.
In the first paper the scorpion was referred to Palaeophonus (the genus to which the other Siluric forms belong), but in the later publication a new genus, Proscorpius, was proposed for it, mainly from the supposed presence of double claws on the walking legs. Scudder [Zittel's Handbuch der Palaeontologie, p. 739] not only accepted this conception but even created a new subfamily, Proscorpionini, which was not brought under the Siluric Palaeophonidae, but under the Carbonic Eoscorpionidae, chiefly because of the supposed existence of double terminal claws on the walking legs.
A year later there appeared in the American Naturalist a critical review by Thorell, of Whitfield's interpretation of certain points in the organization of the scorpion and Whitfield soon after published in Science a general denial of all these points.
When describing the Scottish Siluric scorpion, Pocock in 1901, also discussed Proscorpius osborni, obviously unaware of the criticism by Thorell and of Whitfield's rejoinder, and raised some of the identical points as Thorell, especially in regard to the supposed double claws of the walking leg; and subsequently Fritsch published somewhat fuller notes from excellent photographs made by Dr E. O. Hovey. Fritsch, too, was unaware of Thorell's paper, but he fully verifies Thorell's criticisms. As even the best photograph is misleading through the projection of all parts into one plane and the appearance of deceptive shadows, a close investigation of the specimen itself is essential in order to settle the many debated points and by the courtesy of Dr Hovey we have had full opportunity to study the specimen and to compare it with his photograph. In consequence we have added a third figure and a restoration to illustrate our conception of the fossil.
Carapace. This is subquadrate in outline, a little wider than long. Its front margin is straight and faintly emarginate, appearing trilobed through the projection of the eye lobe in the middle and that of the frontal lobes at the antelateral angles. The eyelobe is relatively large, roundish pentagonal. The frontal lobes are well rounded and project slightly beyond the frontal margin. The left lateral margin is distinctly broken and incomplete, and the right one largely covered by the matrix; nevertheless the anterior portion of the right margin can be distinctly seen to bulge out directly behind the eye lobe, and we have no doubt that the carapace was broader in the middle than in front [see restoration, text fig. 83]. The posterior margin is slightly concave. The surface of the carapace is rather even and smooth and a great number of bristles
Figures 81-83 Proscorpius osborni Whitfield. Figure 81, original figure; figure 82, diagram of cephalothorax and first segment; figure 83, restoration of same. ch, chelicera; pp, pedipalp; l, walking legs; el, eye lobe; le, lateral eyes; me, median eyes; c, comb
Eyes. Whitfield and later Scudder [1886, p. 28] described the lateral eyes as situated on ridges near the antelateral borders, while Fritsch states that he saw three frontal eyes on the left frontal border of the eye lobe and therefore assumes that there may have been six altogether. He was the first to discern the contours of the large median eyes near the posterior margin. A small plain tubercle arising from a shallow depression is situated behind these eyes.
The specimen itself exhibits two distinct ocelli standing out like minute pearls in front of the eye lobe. There are much more minute tubercles on the left side of the ocelli which are of a distinctly different character. There is further seen on the left antelateral lobe of the carapace a small longitudinal series of four tubercles that, from their position and character, may well represent another group of lateral eyes.
Mesosoma. The mesosomatic segments forming the preabdomen have been the principal object of doubt. The upper side of the abdomen is cracked lengthwise; the left side is considered as the dorsal side, the right one as the ventral side by Whitfield and apparently also by Scudder. As a result of this conception of the fossil, it is inferred that the ventral side possessed, in distinction from all other scorpions, six subequal sternites; and as a further corollary, that since these supposed sternites exhibit no stigmata, the species was probably aquatic. Thorell, Pocock and Fritsch have criticized these inferences, and Thorell and Fritsch agree that only the dorsal plates are seen, the supposed ventral plates on the right-hand side being only the impressions of the dorsal plates that are broken away. Thorell bases his view mainly on the fact that the articulations of all the "ventral plates" are direct continuations of the articulations between the dorsal plates, which is not the case in the scorpions. The inspection of the specimen leaves no doubt that the ventral side of the preabdomen is not visible.
Fritsch has inferred from his study of the photograph that one sees indications of the organs of respiration on the right side in the 4th-6th segments. "There are oval bodies," he says, "which correspond to the lung sacs of the scorpions," adding, "Nothing can be observed of openings of these sacs, namely stigmata, to the outside." This inference is due to a deceptive feature of the photograph, in which fragments of the test of the tergites and slight folds give the appearance of oval depressions in the underside of the preabdominal segments.
The tergites are of relatively greater width than those of Palaeophonus, especially P. nuncius. The first is the shortest and the tergites gradually grow in length backward. The anterior and posterior margins are nearly straight, the lateral margins not well seen, owing to the crumbling of the edges. It is obvious, however, that they did not diverge forward as in Palaeophonus or were entirely rounded off as in Eoscorpius but diverged backward to the fourth, which is the widest, then again contracting. The first seems to have been rounded at the posterior angles. The anterior edge of the tergites possesses a transverse, forward sloping, smooth, articulating band which is a rather prominent feature though but faintly seen in the photograph. It does not, however, follow the lateral edges as figured by Whitfield, nor does it exhibit the raised transverse line appearing in the original figure of the species.
Postabdomen. The first metasomatic or postabdominal segment has the form of a truncate cone, as in other scorpions. Of the narrow tail four segments are seen in an impression only. These also have led to some discussion, as Whitfield, in consequence of his conception of the presence of ventral preabdominal plates, inferred that the impression is that of the ventral side of the tail. This side shows only two longitudinal ridges like the dorsal side in other scorpions, and hence the conclusion was reached that the "bending of the tail was downward, not upward, over the back." Against this Thorell has urged that probably the tail, which is detached, has been turned upside down and that now the inside of the dorsal side is seen in the impression. The oblique position of the frontal margin of the tail to the posterior margin of the first postabdominal segment, and the lateral position of the two carinae of the first tail segment serve to show that the tail is out of its original position, and that therefore no inferences as to the character of the dorsal and ventral sides can be drawn from its present position.
Appendages. The appendages present the greatest difficulties to a correct interpretation on account of their unfavorable preservation arid small size. We find, accordingly, wide differences in the views held by the authors concerning them.
One of the two chelicerae has been pushed forward and is seen in front of the carapace. Its distal portion is preserved only as an impression and but a portion of one finger is noticeable. The proximal portion of the powerful second joint is preserved as a flattened tubular body, distinctly broken off in front. Fritsch has interpreted this part as the manducatory lamella of the coxa (Kauglied), and states that it shows a short curved claw at the anterior margin. Inspection of the specimen, however, shows readily that the hand of the chelicera is the direct continuation of this proximal part, and that the latter lies upon the coxa of the pedipalp. The short claws are not visible in the specimen and Fritsch's representation is apparently due to shadows produced by irregular depressions between the lost anterior and the preserved posterior portions of the chelicera.
The greatest difficulty is presented by the legs, since these appendages are piled together in one place and badly torn. They have therefore been very differently interpreted and caused much of the controversy about this scorpion. The second joint of the left pedipalp (trochanter) is seen as an impression at the left of the base of the chelicera, which it underlies. The third joint (humerus or femur) stands, as in other scorpions, at right angles to the trochanter and partly underlies the left side of the carapace. It is broader and longer than represented by both Whitfield and Fritsch. It is partly broken off where one of the walking legs underlies it. Whitfield [op. cit. pl. 20, fig. 1, 3] represents this joint as directly connected with the chela or hand of a pedipalp seen in the specimen, by a short fourth joint (brachium or tibia), but Fritsch sees in this connecting broken film "a triangular sternum on which one discerns no further details," and "two oval opercular plates," adding that both organs agree with those which he has figured from the recent Buthus. We have been unable to notice in the place where Fritsch figures the triangular sternum anything but a faint, irregular discoloration, such as is seen in many places on the slab. This appears too dark in the photograph and is therefore misleading. The opercular plates are more irregular in outline than would appear in the photograph, but the fact that they overlie the legs (hence lay inside of the same in the specimen), and their relative position to the comb which lies nearby, suggest the possibility of their representing the opercular plates.
The hand or chela in the specimen probably does not belong to the left pedipalp, as inferred by Whitfield, for from the crushed character of the "palm" of this hand we infer that it was the strongly bulging inner side, turned upward, and hence is the right chela thrown over on the left side. This inference is supported by the two strong joints which extend from the chela toward the posterior part of the carapace and are too broad and strong to have been joints of walking legs, as represented by Whitfield. The left chela and tibia are probably folded under the body.
The pedipalp of this scorpion was clearly a powerful organ and exactly corresponded in relative size to the pedipalp of recent species.
Of the walking legs but one projects beyond the confused mass of limbs. This has been the subject of much controversy. Both Whitfield and Scudder believed a double claw to be observed at the supposed terminal joint of this leg. Since the other Siluric scorpions, the species of Palaeophonus, are distinguished from all later scorpions by a single, spinelike claw, they rightly saw in this feature an important character connecting Proscorpius with the Carbonic and recent scorpions. For this reason Scudder created the subfamily Proscorpionini, which he placed under the family Eoscorpioidae, the Palaeophonoidae forming the other family of the older Anthracoscorpii. Thorell soon after pointed out that a close inspection of the figures gives the impression that the leg in question is incomplete, "being broken near the base of one—probably the last—of the joints" and "that the 'bifid' ending of the leg on the figures does, in fact, not at all give the impression of two claws, but resembles closely the also broken end of the right leg of the last pair in the figure of Palaeophonus nuncius Thor. & Lindstr." Other reasons are cited by this eminent authority on the scorpions in favor of the closer relationship of Proscorpius with Palaeophonus, notably the cylindrical character of the joints, while in the later scorpions the tibia is compressed and convex longitudinally on the under side; and, also, the comparatively short joints of the legs. Pocock expressed similar doubts in stating [1901, p. 309] that "the apical segment of the leg is simply bifid at the tip, a feature which may be due to fracture, or may represent a pair of sclerites like those borne at the tip of the distal segments of the fourth leg of Limulus, or may be explained on the supposition that the end segment terminated in a sharp point as in Palaeophonus, and was furnished near the tip with a movable spine or spur." Pocock further points out "that there is no agreement between Scudder and Whitfield as to whether the segment stated to possess these claws is numerically the third or sixth from the base," and that further discussion of the matter is therefore idle. According to Scudder's interpretation the claws would be at the end of the third or fourth segment and are therefore not to be compared with the tarsal claws of other scorpions which were at the seventh joint.
Fritsch has raised the same objections as Thorell to Whitfield's and Scudder's view of the presence of two terminal claws, considering them as due to the wrong interpretation of fragments and pointing out that the tarsal joints which would carry the claws, must be much smaller.
The disagreement between two such trained observers as Scudder and Whitfield as to the number of joints is probably the best proof of the very unfavorable state of preservation of the leg in question, which, in fact, is in its distal portion but a faint impression, precluding positive assertions. Our view is that only the articulations drawn in by Scudder are such, since along them the joints are slightly set off, one of the other lines being the margin of the palpus pressed through the joint of the leg; and that the "claws" are torn fragments of another joint, the latter being especially suggested by their blunt, unequal, triangular form, in contrast to the hooklike form of the double claws of the later scorpions, and the
|Figure 84 Restoration of dorsal side of Palaeophonus nuncius Thorell & Lindström. (From Pocock)||Figure 85 Restoration of ventral side of Palaeophonus hunteri Peach. (From Pocock)|
fact that their outer edges lie in the direction of those of the preceding joint. The leg, if complete, would also be relatively too short.
Scudder has also drawn a small spine at the base of the "penultimate" joint, which Whitfield [p. 187, footnote] states he has been entirely unable to find. We have also failed to find in this place more than a faint, uncolored impression that is probably accidental. Palaeophonus bears a spine in a corresponding position on the second tarsus, and this fact may have induced Scudder's inference.
Although the presence of the two "claws" on which the separation of Proscorpius from Palaeophonus was mainly based [see Whitfield, p. 183] may be wholly illusory, Proscorpius is nevertheless a good genus. This is evinced by the marginal position of the eye lobe and the greater width and different lateral margin of the tergites. The general form of the carapace and the character of the legs, as far as perceivable, indicate that its closest relationship is with the other Siluric scorpions.
There are still two joints of another leg distinguishable on the left side. The three legs drawn by Fritsch on the right side of the carapace are due to deceptive shadows on the photograph, produced by irregular organic patches that lie in a higher layer of rock and apparently have nothing to do with the scorpion. It is desirable that this covering matrix be removed and a possibly complete right margin of the carapace exposed.
Fritsch was the first to observe the portion of the comb discernible on the left side. The specimen itself shows the fragments still more distinctly than the photograph, because the surface bearing them slants away from the light. Fritsch recognized fulcra and comb teeth and states that these remains indicate that this organ was of similar structure as in the younger scorpions.
The inspection of the specimen in good light has brought out the interesting fact that the test distinctly retains the bristles with which it was covered. They are most distinctly seen, and also thickest, on the carapace, but also visible on the tergites. The photograph fails to show them.
We may be allowed to touch upon the fascinating question of the original habitat of this waterlime scorpion, even though it can not, in the absence of the ventral side, furnish any direct evidence as to its mode of breathing.
Whitfield inclined to the view that the creature was aquatic mainly because he failed to find the stigmata on the supposed ventral plates. Thorell and Lindström considered Palaeophonus nuncius, in which they observed a possible stigma on the ventral plate, as an undoubted air breather and have acclaimed this as the most important proof of a Siluric terra firma, with an air-breathing fauna. Laurie, in describing Palaeophonus loudonensis says [1899, p. 576] it does not necessarily follow that this scorpion was an air breather, since "the characters which mark it as a scorpion may well have been developed before the terrestrial mode of life and consequent modification of the respiratory organs took place." He adds that "unfortunately these respiratory organs are necessarify so delicate in texture that we know very little of their structure and arrangement in any of the fossil Arthropoda"; and Pocock [1901, p. 305] shortly after Laurie, argued that the Swedish P. nuncius lacked the stigmata, considering the stigma or spiraculum described by Thorell as a fortuitous crack in the integument, the part of the plate exposed belonging, according to his interpretation, not to the third mesosomatic somite, but to the second, which bears no stigmata in the scorpions. Pocock goes further and claims that the last two plates of the mesosoma of P. nuncius, considered by Thorell as tergites, are sternites and fail to show the stigmata which constituted Thorell's reasons for considering them as tergites. Pocock also failed to find the stigmata in P. hunteri, which Peach thought to have seen, and, believing that this Scottish specimen exposes the ventral side, he assumes a sceptical attitude to the presence of stigmata in the Siluric scorpions. The idea that the Siluric scorpions lived on land, he says, is "less easy to reconcile with the facts that both the known specimens are relatively in an admirable state of preservation, and were met with in strata of undoubted marine origin, containing abundance of admittedly marine organisms, than the belief, which I hold, that Palaeophonus lived in the sea, probably in shallow water, its strong sharply pointed legs being admirably fitted, like those of a crab, for maintaining a secure hold amongst the seaweed or on the jagged surface of rocks, and for resisting the force of the rising and falling waves."
We have seen above that Fritsch believed there were indications of lung sacs in Proscorpius osborni, but inspection of the specimen has failed to reveal any traces of respiratory organs.
Although the discussions of the authors cited demonstrate that the ventral side of the mesosoma is not shown well enough in any of the four Siluric scorpions to settle the question of the presence or absence of stigmata or the life habit of these scorpions, we feel that Whitfield's, Laurie's and Pocock's suggestion of their probable aquatic habitat is well worthy of serious consideration. It is therefore pertinent to summarize here the arguments in favor of this view.
1 All four scorpions have been found in marine beds and in such good preservation that it is difficult to assume they drifted out to sea; especially since the beds containing them do not afford any other remains of land animals or plants. On the other hand, we should note in this connection that they all four occur in association with eurypterids, and these are considered in this publication as having been principally inhabitants of estuaries. But this association may, as indicated under 3, have rather a phylogenetic than a physical cause.
2 If the Siluric scorpions agree with the recent ones in respect to the body form and arrangement of the prosomatic appendages, then it does not follow, as pointed out by Laurie [loc. cit. p. 577], that they have reached the same point of specialization in respect to their respiratory organs. "The terrestrial mode of life and consequent adaptation to airbreathing may have come later."
3 As Pocock has shown that the arrangement of the parts constituting the ventral side of the prosoma in Palaeophonus indicates that the latter "occupies an intermediate position between Limulus and the Eurypterida on the one hand, and recent scorpions on the other, standing, if anything, rather nearer to the former than to the latter"; it is probable that Palaeophonus and the closely related Proscorpius still shared an adaptation to water-breathing with their nearer related ancestors and relatives.
Figure 86 Fourth leg of a recent scorpion (Buthus australis). (From Pocock)
Figure 87 Third leg of Siluric scorpion, Palaeophonus nuncius. (From Pocock)
sp, spurs and lobate sclerites; ?sp, processes possibly representing the point of attachment of spurs in Palaeophonus; cl, claws 4 This suggestion is further strongly supported by the very primitive character of the walking legs of the Siluric scorpions and the fact that they appear better adapted to a marine life than a terrestrial one, as pointed out by Pocock. In fact the legs of Palaeophonus [text fig. 87] are so much like those of the eurypterids that they at once suggest a like use, and a like habitat of the animal; hence a different one from that of the later scorpions.
5 In view of the latter suggestion, the fact of the association of the Siluric eurypterids becomes significant in indicating that these similar creatures had also a similar mode of life and the same habitat. If they were still as nearly related as Pocock asserts, it is proper to assume that the two diverging branches had not yet sought different fields of action.
6 The possibility of a creature of the shape of the Siluric scorpion finding congenial conditions in the waterlime sea is clearly brought out by Eusarcus, which bears, especially in its earlier growth stages, a striking resemblance to the scorpion [pl. 36, fig. 1] as evinced by its specific name scorpioides, and that of the British congener, E. scorpionis. We have little doubt that Eusarcus and Proscorpius were close competitors in the same field. Through these Eusarci, proscorpius and Palaeophonus become also in aspect integral elements of the eurypterid waterlime fauna.
7 As Eusarcus and the Siluric scorpions are so much alike in their body form, they may be assumed to have had similar habits, and it follows that these scorpions were probably also given to burying themselves in the mud, waiting there for their prey as undoubtedly many of the eurypterids, and especially Eusarcus, did. In this connection the fact becomes extremely significant that Palaeophonus nuncius was blind, according to Thorell and Lindström's observations, and that, for this reason, Lindström [1855, p. 8] infers some difference in habits from those of the recent scorpions, and believes that it may have possessed a burrowing mode of existence.
It would be singular indeed if, of all the Siluric terrestrial fauna, the scorpions alone should have been repeatedly carried out to sea in a good state of preservation; much more plausible is the assumption of their coexistence in the sea with the similarly constructed and closely related eurypterids, with which their remains are found associated.
The genus Hastimima White
David White has described [1909, p. 589] under the name Hastimima whitei certain fragmentary remains from the Carbonic plant beds of Santa Catherina, Brazil, as doubtful plants, but under protest, as it were, after various paleontologists had failed to recognize them as belonging to any other group. Seward [1909, p. 484] has referred a similar fragment from the Witteberg series of South Africa to Hastimima, suggesting that it represents part of a body segment of an eurypterid. This suggestion was fully verified by Henry Woodward after inspection of the specimen. This pioneer and leader among the investigators of eurypterids, has also subjected White's photographs of the Brazilian types to critical notice [1909, p. 406], and has recognized the two largest fragments as parts of a segment and a telson of an eurypterid, referring them tentatively to Pterygotus; and the smaller fragments as portions of segments, the sculpturing of which recalls that of certain later species of Eurypterus, such as E. punctatus and E. hibernicus. He suggests that the Brazilian material of Hastimima includes specimens of more than one species, if not of more than one genus.
Figure 88 Hastimima whitei White. Fragment of tergite. Natural size
Through the courtesy of the National Museum, we have been enabled to study the Brazilian specimens of Hastimima and have derived the following notes on these interesting fossils.
The material, although fragmentary, includes three specimens that may be referred without doubt to parts of the integument of an eurypterid and these we describe more fully.
One is a portion of a segment, another of the telson and a third a proximal part of a leg with the coxa.
The fragment of a segment is represented by White's figures 1, 1a, and 2 of plate 10.
The first [text fig. 88] is a subtriangular fragment bounded on two sides by the original margins that meet in an acute angle. One of these margins is much thickened and produced at an angle into a falcate lobe; and the other is marked by a distinct darker band obviously representing a doublure. The thickened margin shows different surface sculpturing on the two surfaces that are separated by matrix, and is also due to a doublure. From the direction of the droplike surface scales or spines and the form and direction of the lobe at the angle, as well as the presence of the doublures on the margins, we infer that the fragment is the postlateral portion of a segment. From its angular form we further infer that it belongs to a tergite and from the fact that the lateral thickened margin rapidly diverges in posterior direction from the main axis, that it was an anterior tergite and also that the preabdomen of this species must have rapidly expanded, as in Eusarcus.
The ornamentation is distinctly eurypteroid. It consists of widely separated, rather irregularly distributed, blunt or club-shaped spines; on the body of the tergite of closely arranged oblong to angular interior thickenings of the upper test of the thickened lateral margin, and one row of subangular impressed scales, probably originally spines, along the posterior margin. The scales of the lateral margin are also impressed on the cast of the underside of the integument and consisted of local thickenings.
The second determinable fragment is the posterior portion of the telson. Its detail is well shown in White's photographs [op. cit. pl. 10, fig. 3, 4]. It is acutely hastate in outline and of somewhat complicated structure. Our conception of it as obtained from the relievo and intaglio specimens, is best understood by the diagrammatic transverse section, text figure 92. It consists of two separate laminae. One of these is covered with the large droplike scales as on the rest of the integument and for this reason is considered by us as the dorsal lamina. The other is smooth. The interspace between the two is occupied by rock, as shown by a patch clinging to the dorsal side. The dorsal side was of one uninterrupted lamina, as is well shown at the proximal end of the intaglio; the ventral side, however, consisted of two laminae, separated by a median cleft. This is distinctly shown by the proximal and distal ends of the specimen [text fig. 90]; at the
Figures 89-93 Hastimima whitei White. Figure 89, dorsal view of telson; figure 90, ventral view of telson; figure 91, transverse section of proximal end of telson; figure 92, restoration of transverse section of telson; figure 93, coxa, with several attached leg segments. Natural size
Figure 94 Eurypterus? Salter, from Coal Measures at the Joggins, Nova Scotia
Along the median line of the middle plate, just above the median ventral cleft, a suture passes. The presence of the cleft and of the middle plate with the median suture, all combine to suggest that the two halves of the broad telson may have been capable of being bent slightly in the back stroke of the napping telson.
The margin of the telson has a thickened rim which is cracked at irregular intervals, as in Eurypterus, giving it a serrate appearance.
The third fragment is the proximal portion of a leg [text fig. 93]. It retains the coxa with the gnathobase and portions of the three succeeding segments. The form of the coxa would indicate that it belongs to an endognathite. Its form is elongate quadrangular; the manducatory edge is slightly curved and bears a series of nine or more, rather blunt teeth, which become natter posteriorly. The part adjoining the manducatory edge is furnished with a pavement of flat polygonal scales which are elongate and slightly imbricated near the anterior edge. The rest of the coxa bears small subcircular flat scales and minute tubercles.
The outlines of the following segments of the leg are very faint and can be made out only with difficulty by turning the specimen to the light. The surface of these segments is finely granulate.
Besides these three more important fragments there are small patches of lobate fringes such as the posterior margins of the tergites of the later eurypterids frequently exhibit. Their variation in length and form, as well as their characteristic sculpturing, are shown in White's photographs, reproduced on his plate 11, figure 2, 2a, 6-10. The smaller of the lobes, which are invariably blunt and closely arranged, are smooth on the underside and show the impression of spines or short bristles on the other. The adjoining integument shows a pavement of polygonal scales similar to those observed on the gnathobase of the coxa. The largest lobes reproduced by White in figure 2, 2a of plate 11 are rounded and thick and represent a radiating group of stout, hollow processes. These are also covered with oblong, umbilicate impressions, obviously the molts of imbricating plates with perforations that probably were connected with spines.
We may point out in this connection that Salter in 1862 [p. 78] described as Eurypterus (?) from the Coal Measures at the Joggins, N. S., the proximal portion of a telson which seems to be a fair expression of the posterior portion of such a telson as that of Hastimima whitei, even down to the suture of the median carina. We introduce here [text fig. 94] a copy of the Joggins specimen with the outline restored to correspond to that of the telson of Hastimima. This telson fragment is associated with fragments of segments bearing the characteristic thick, drop-shaped or club-shaped tubercles of the later eurypterids. It has been kindly loaned to us by Professor Frank D. Adams from the Redpath Museum of McGill University. We agree with Salter "that it can hardly be supposed to be other than the caudal joint (broken) of an Eurypterus or allied form." It is evident from the specimen that there was an elevated median part, apparently with a sulcus in the middle, flanked by two lateral wings with a flat border.
The Brazilian fragments of the segment and telson are so much alike in their ornamentation that they are safely referred to the same species and genus and properly considered as the type specimens of the eurypterid Hastimima whitei, and it is probable that this generic term will have an independent value, for though the telson in its outline is certainly comparable to that of certain species of Pterygotus, as P. minor Woodward, its section is totally different from that of any of the Pterygotidae and the fragment of segment indicates a different inclination of the side of the body than is observable among other pterygoids.
Note on Sidneyia inexpectans Walcott
Among the remarkable remains which have been described by Dr C. D. Walcott from the Cambric is a wonderful arthropod Sidneyia inexpectans, which has been brought to public notice just as this work is completed.
This organism is extraordinary in the preservation of its anatomy and as both it and its associate, Amiella ornata, are referred by Dr Walcott to the Merostomalta, they invite brief notice in this place. Both are from the Middle Cambric (Stephen formation) of British Columbia.
Amiella ornata is based on a fragmentary portion of an abdomen and for this reason will not be included in our annotations. These refer entirely to the splendid material secured of the species Sidneyia inexpectans.
Sidneyia and Amiella are united in a new suborder Limulava of the Eurypterida.
The suborder is described as follows:
Body elongated with a thin epidermal skeleton either smooth or ornamented by lines or ridges. Cephalothorax with lateral or marginal eyes, on the ventral side with five pairs of movable appendages; mouth posterior to a large epistoma.
Abdomen with twelve segments, the anterior nine of which have a pair of ventral appendages to which the branchiae are attached; the posterior segment has a central spatulate-shaped section that, combined with swimmerets, forms a strong caudal fin.
The description of the branchiae will be found under the description of Sidneyia, the typical genus of the Limulava.
Observations. The suborder Limulava differs from the Eurypterida, to which it is most nearly related, in having a large epistoma similar to that of the Trilobita; in not having a metastoma, chelate antennae, and swimming cephalic appendages; and in having a broad, fan-shaped caudal fin, and branchial appendages more or less unlike the lamellar branchiae of the Eurypterida and Xiphosura.
The relations of the order and suborder are shown in the following tabular view:
|Order Eurypterida||Suborder Limulava|
|1||Cephalothorax long||1||Cephalothorax short|
|2||Cephalothorax with six (6) pairs of appendages; the anterior pair chelate antennae, and the posterior pair, long, strong swimming legs||2||Cephalothorax with five (5) pairs of appendages; the anterior simple antennae, the third pair multichelate, and the posterior pair short, the outer joint serving as a branchial organ|
|3||Epistoma present in Pterygotus where it is narrow. Metastoma large||3||Epistoma large. Metastoma unknown|
|4||Six anterior abdominal segments bear leaflike branchial appendages||4||Nine anterior abdominal segments bear leaf like branchial appendages|
|5||Surface of test with scalelike ornamentation||5||Surface of test smooth or with imbricating lines, as in many of the Trilobita|
|6||Terminal segment a simple lanceolate or spatulate telson||6||Terminal segment a caudal fin formed of a central expanded telson and one or more swimmerets on each side|
In view of the unusual structures here set forth it is germane to this work to inquire whether these Limulava should be construed as belonging to the Eurypterida in the capacity of a suborder or if they may not more properly assume a higher grade as an independent and coordinate group.
The Eurypterida, as represented by the genera hitherto referred to them, constitute a very compact order with well fixed characters. If we place the Limulava with them their definition has to be completely changed.
In the Eurypterida the cephalothorax bears six pairs of appendages, the first of which are chelate antennae or chelicera; these are apparently absent in Sidneyia inexpectans, where there are only five pairs, the first of which consists of simple antennae. In Slimonia the corresponding pair of legs is also tactile and the antennae of Sidneyia apparently bore coxae, so that the character of the first pair of legs would not constitute a difference of more than generic value. Chelicera, however, are characteristic of the Eurypterida, and if Sidneyia is an eurypterid, it is to be assumed that these, often delicate organs, will be found on further research. The third pair of legs is one of the remarkable features of this organism. It is described as "multichelate," or as possessing "broad, strong joints in small specimens, and in large specimens it is developed into peculiarly constructed and complex chelate terminal sections; this is formed of twelve or more joints of a forward curving appendage to which are attached on the anterior side long spines carrying numerous smaller spines on the margin opposed to the main body of the appendage." If indeed the leg consists of two jointed appendages, as reproduced in op. cit. pl. 4, figures 1 and 4, then we have here a biramous leg such as would be characteristic of the Crustacea in contrast to the Merostomata, and a feature which indicates that the fossil is a crustacean rather than an arachnid. The long bladelike appendages resemble those of the legs of Stylonurus excelsior and Echinognathus clevelandi and might, like the latter, have served to make a swimming organ of the third pair of legs. There is still a bare possibility that they are analogous to the male clasping organ observed by Holm on the second walking leg of Eurypterus fischeri and which had a sexual function. However that may be, these complex legs of Sidneyia are important in showing a certain advanced adaptation of the genus in the form of these organs. The last pair is described as short and bearing an outer, broad joint or palp fringed with five branchial setae or spines. This is another character entirely foreign to the arachnids and ascribable to the crustaceans.
The carapace is stated to possess a large epistoma and to lack a metastoma. In eurypterids the epistoma is only known in the Pterygotus-Slimonia group. It is there a separated part of the marginal shield and originated from a part of the carapace being bent over, as shown by the direction of the sculpture. The organ figured as epistoma of Sidneyia (op. cit. pl. 5, fig. 3) is hardly comparable to the epistoma of Pterygotus, as it is not separated by sutures from the marginal shield. The view referred to is obviously a dorsal one and there seems to us much probability that the large "epistoma" may prove to be the anterior part of the carapace pushed out of position.
There is nothing visible in the figures of these finely preserved remains to suggest the presence of a metastoma. The latter is distinctly a characteristic and important organ of the order Eurypterida. If it is actually absent in the Limulava this fact would militate against the inclusion of the latter in the eurypterids.
The most important differences between the Eurypterida and Limulava appear, however, in the constitution of the abdomen. The abdomen of the Eurypterida consists invariably of six tergites on the dorsal side, to which correspond five sternites on the ventral side, and six ringlike postabdominal segments. Sidneyia, however, appears to possess as many segments on the dorsal as on the ventral side. The operculum or first ventral plate which covers both the first and second segment and which bears the genital appendage, was hence not yet developed. This would be a most primitive condition, as compared with the eurypterids, and constitutes a difference of ordinal rank. Sidneyia is further described as bearing branchiae on nine segments. The Limulava have accordingly nine abdominal segments and but three postabdominal segments, for the gill-bearing ventral segments must be movable plates of the character of sternites. This is also a difference of ordinal rank, for the number and division of segments in the Eurypterida is absolutely fixed, but if Sidneyia is in any way related to the ancestral stock of the Eurypterida it is bound to throw most interesting light on the morphogeny of the abdomen. The gills themselves must also have been different from those of the eurypterids. As a rule the eurypterids show only the attachment areas of the branchiae, but the gills themselves are, as in Limulus, extremely delicate, leaflike appendages visible only under the most favorable conditions, when separated from the body. The gills of Sidneyia as figured lack the thickened attachment scars and are themselves of such size as to overlap several sternites (op. cit. pl. 2, fig. 1; pl. 6, fig. 3), all features that are not found in the eurypterids or Limulus.
The most picturesque feature of the Sidneyia is its fanlike tail, consisting of the last segment and one or more swimmerets on either side. The development of such a tail fin is not entirely absent in the Eurypterida, as evidenced by the bilobed tail of Erettopterus, but it is the telson spine in the latter genus which assumes the finlike form, while here the swimmerets are attached to the anterior side of the last segment. The telson spine is therefore apparently not developed in Sidneyia and it would seem possible that the swimmerets are a further development of the lateral lobes of the last segment. We infer from figures 2 and 3, plate 3 of Mr Walcott's paper that they may even have been articulated. As pointed out by Mr Walcott, this telson is like that of the Macrura and it is a feature foreign to the eurypterids.
It seems to us probable that the Limulava as described are not eurypterids, but constitute a primitive order, though exhibiting some remarkable adaptive features. This order possibly belongs to the Merostomata but it is distinctly allied to the crustaceans in such important characters as the structure of the legs and telson, and is therefore much generalized.
Mr Walcott has rightly pointed out the similarity in the carapaces of Strabops and Sidneyia and suggests that Strabops may have but five pairs of cephalothoracic appendages. Strabops, however, has the eyes and telson spine of an eurypterid and the similarity of the carapaces is probably due to the primitive nature of both genera.
EURYPTERIDS FROM THE NORMANSKILL SHALE OF NEW YORK
After the foregoing discussion of the Frankfort shale eurypterids had been prepared our attention was directed by Professor G. H. Chadwick to similar remains which he had observed in the sandstones of the Broom street quarry at Catskill, N. Y. The only fossils heretofore known from the so called "Hudson River beds" about Catskill are the Normanskill graptolites, indicating horizons of Upper Chazy age, and the presence of eurypterid remains in this early stage was a matter of so much interest as to justify a careful examination of the locality.
The lithologic and faunal conditions at the Broom street quarry exposure were found to be a singularly complete duplication of those of the eurypterid-bearing exposures in the bluestone quarries at Schenectady. The Broom street quarry is also a bluestone quarry, the rock being mostly used in the crusher. The courses of "bluestone" (here an impure argillaceous sandstone) are very compact, from 3 to 30 feet thick between the intercalations of black shales. There is distinct evidence of shallowwater conditions, one bed being conglomeritic and largely composed of pebbles, many of which appear to be mud pebbles; another beautifully exhibiting very regular, widely separated wave marks with winnows of comminuted seaweeds and eurypterids in the troughs.
Quite as in the bluestone quarries of the Schenectady beds, the surfaces of some of the sandstones are densely covered with rather poorly preserved seaweeds and eurypterids. It was therefore natural to expect that here too the black intercalated shales would contain better material of these fossils and possibly also graptolites that would indicate the age of the beds. They have indeed afforded a layer with an association of finely preserved seaweeds, the eurypterids herewith described, and the following graptolites: Dicellograptus gurleyi Lapworth, Climacograptus bicornis Hall, Climacograptus bicornis var. peltifer Lapworth, Cryptograptus tricornis (Carruthers), the first three forms in great abundance. This graptolite association is one of undoubted Normanskill age. The seaweeds occur in large perfect fronds and are of the same type as those in the Schenectady shale. The eurypterids also are strikingly similar to those from the Schenectady beds.
In one case (Pterygotus ? nasutus) we have been unable to distinguish the Schenectady and Normanskill types. This striking similarity of the two faunas (one of Chazy, the other of Trenton age) amounting almost to identity, seems to indicate a very slow progressive development of the eurypterid faunas, probably owing to their early adaptation to particular marine conditions. Similar stability of the eurypterids is also suggested by the identity or extremely close relationship of the species in the Shawangunk grit at Otisville and the possibly older beds at the Delaware Water Gap and Swatara Gap [see p. 417] in Pennsylvania; and again in the probably somewhat younger McKenzie formation of Pennsylvania [see p. 88], and finally also by the continuation of the same genera apparently from the Ordovicic, but surely from the Siluric into the Carbonic. The eurypterids are then, as a rule, to be accorded but little value for purposes of correlation.
The following species are quite obviously but a meager part of the eurypterid fauna of the Normanskill stage, and future discoveries, now that the attention of collectors is directed to these interesting fossils, will undoubtedly add much to the list. As in the Schenectady shale the generic determinations are entirely provisional, as but few legs and telsons have been found in connection with the carapaces and fragmentary abdomina.
Eurypterus chadwicki nov.
See text figure 95
Fig. 95 Eurypterus chadwicki nov. Holotype. ×1.5 Carapace semioval to semicircular; lateral and frontal margins forming a uniformly rounded curve; length to width as 2:3; basal margin straight transverse. All margins apparently with a broad flat border. Lateral eyes large, about one fourth the length of the carapace, elliptical in outline, prominent, situated forward, in front of the middle transverse line, less than their length distant from the margin. Length of carapace of type, 11.6 mm; width, 16.2 mm.
Eusarcus linguatus nov.
See text figures 96, 97
Carapace semioval, with a tonguelike process in front; length to width as 4:5. Lateral margins moderately convex; frontal margin produced into a squarish process with rounded anterior angles; one fourth the width and one eighth the length of the carapace; basal margin slightly concave, the postlateral angles subrectangular.
Fig. 96, 97 Eusarcus linguatus nov. Fig. 96 Holotype. × 2. Specimen somewhat disorted. Fig. 97 Cotype. × 1.5. Younger individual showing traces of the sculpture, the frontal process and the ocellar mound Eyes marginal, circular, small, a little longer than one fifth the length of the carapace, situated in an angle between the lateral margins and the base of the frontal process. Surface densely covered with relatively large flat nodes. The type measures 9.4 mm in length and 10.5 mm in width.
This species strongly suggests the Eusarcus vaningeni, with which it has not only the peculiar anterior snout in common, but also the general outline and the position of the eyes. It is also closely related to the species here described from the Normanskill and Schenectady shales as Pterygotus? (Eusarcus) nasutus, which possesses a less prominent anterior process and more distant eyes but is very similar to this species in outline and surface ornamentation.
We also refer to this species a number of specimens which correspond to the above description in all particulars but lack the anterior process and assume that the latter may either be broken off or be folded under normally like the epistoma of Pterygotus; with present material we have no means of deciding which.
Dolichopterus breviceps nov.
See text figure 98
Fig. 98 Doli-
chopertus breviceps nov. Holotype.
× 3 A small carapace differs from the others in the position of its lateral eyes which are submarginal in the antelateral angles, thereby suggesting the presence of a species of Dolichopterus. The carapace is rather short subquadrangular, its length to its width as 5:7; the lateral margins slightly concave, diverging forward at a small angle, the frontal margin broadly convex, the antelateral angles prominent, well rounded; the basal margin straight transverse. The lateral eyes are large, a little more than one third the length of the carapace, subcircular, situated as stated. The type is 4.7 mm long and 5.5 mm wide.
Stylonurus modestus nov.
See text figures 99-101
This species is based on several small carapaces with portions of the abdomen and a leg [see text fig. 99] which suggest the following description:
Fig. 99-101 Stylonurus modestus nov. Fig. 99 Holotype. × 2. Specimen showing carapace, with broad border, portion of walking leg and of abdomen. Fig. 100 Small well preserved carapace, showing the subcircular eye nodes. Cotype. × 2. Fig. 101 Specimen with similar carapace to preceding, broad border, large eye nodes, and very slender abdomen. Cotype. × 2 Carapace subrectangular, broad, length to width as 5:8. Lateral margins nearly straight, slightly converging forward, anterior margin gently emarginate in the middle, posterior margin straight transverse. Lateral eyes very large, between one half and one third the length of the carapace, circular, situated subcentrally, as far apart as their length. Basal margin straight transverse. Lateral and anterior margins with a broad thick border, probably originating from a doublure on the underside. Body slender, hardly expanding posteriorly and gradually contracting to postabdomen. One leg [see text fig. 99] observed which appears to consist of spineless tubular, striated segments, as in Stylonurus. Length of carapace of type [text fig. 99], 5 mm; width, 7.5 mm.
We have referred this species to Stylonurus rather than to Eurypterus on account of the aspect of the carapace, with its broad border, large eyes and broad, subrectangular outline; the slender form of the leg which resembles the posterior walking leg of Stylonurus.
Pterygotus ? (Eusarcus) nasutus nov.
See text figures 102, 103
A number of carapaces from Catskill fail to show any distinguishing features from Pterygotus? (Eusarcus) nasutus (described on p. 382) from the Schenectady beds at Schenectady, and we therefore refer them to that species, although the considerable difference in
Fig. 102, 103 Pterygotus ? (Eusarcus) nasutus nov. Two carapaces showing the characteristic angular front and the position of the eyes. Fig. 102 × 2; fig. 103 × 1.5 age between the forms makes it somewhat improbable that they are conspecific. The sculpture is well shown in several specimens and consists of flat closely arranged rather large nodes or tubercles, as in Eusarcus linguatus. A like sculpture is shown in some of the specimens from the Schenectady shale. In the first description the species is assigned to Pterygotus, but the closely related species from these Normanskill shales, Eusarcus linguatus, indicates that it may more likely be an Eusarcus.
Pterygotus normanskillensis nov.
See text figure 104
This name is proposed for carapaces of distinctly pterygotoid aspect.
Fig. 104 Pterygotus normanskillensis nov. Holotype. × 1.5. The parallel lines indicate the cleavage lines appearing in the carbonaceous film Carapace broadly subrectangular, three fourths as long as wide; lateral margins subparallel, slightly convex, antelateral angle distinct, abruptly rounded; anterior margin broadly and evenly convex. Basal margin slightly concave in middle, postlateral angles approximately rectangular. Lateral eyes marginal, situated in the antelateral corners, elliptic, small, less than one fourth the length of the carapace. Surface sculpture not seen. Measurements of type specimen, length, 11 mm, width, 15 mm.
The presence of a genus of the Pterygotus group
Fig. 105-7 Fragments of Pterygotidae. Fig. 105 Swimming leg. × 2. Fig. 106 Telson of a true Pterygotus. Fig. 107 Probably of an Erettopterus. Both × 2 is also attested by telsons, some of which indicate a true Pterygotus [see text fig. 106] while others suggest forms of Erettopterus [see text fig. 107]. We also figure with these a swimming leg, possibly belonging to this group.
EURYPTERIDS FROM THE SHAWANGUNK GRIT IN PENNSYLVANIA
On a previous page  reference is made to the occurrence of obscure eurypterids in the Shawangunk grit of the Delaware Water Gap, Pennsylvania. The material we then had proved indeterminable, but since then through the courtesy of Professor Gilbert van Ingen we have had opportunity to examine a very large number of specimens from the same locality recently acquired by him and Mr J. C. Martin. In regard to the horizon Professor van Ingen writes:
These eurypterids are from the third quartzitic conglomerate, "Medina white conglomerate, no. 2" of section B, at Delaware Water Gap, which is published as plate I, 1882, Report G6 (Second Pennsylvania Geological Survey). They come from about the middle of this band, and occur in thin seams of black shale of very irregular extent horizontally and of variable thickness and character vertically. Some of the shale seams have none, others abound in the eurypterids.
It thus appears that the occurrence of the eurypterids at the Delaware Water Gap is the same as that in the Shawangunk grit at Otisville.
Unfortunately the maceration, already so prevalent in much of the eurypterid material at Otisville, has at the Delaware Water Gap reached such a destructive degree that the shale is filled with a mass of comminuted eurypterid fragments; and to complete the destruction the chitinous substance has also been chemically altered until it has a slickensided and silky appearance and for the greater part has lost all trace of sculpture. Owing to this extremely unfavorable condition of the material, only a few small carapaces and patches of integument warrant description, although there is plenty of evidence that the eurypterids in these waters of the Shawangunk sea reached considerable size and occurred in great profusion.
The best specimens are identical or very closely related to the following species from Otisville:
1 Dolichopterus otisius Clarke. A number of carapaces with the characteristic subtrapezoidal outline. Three of these, at least, show the position of the compound or lateral eyes and the marginal doublures.
2 Eurypterus maria Clarke. Carapaces with the very uniformly rounded outline of that species but not exhibiting the eyes.
3 Stylonurus cf. myops Clarke. Its presence is suggested by a patch of integument with the peculiar sculpture of that species. The sculpture resembles especially that of plate 53, figure 2.
4 Hughmilleria shawangunk Clarke. A segment with the characteristic linear sculpture. Also several carapaces are referable to this species.
5 Pterygotus cf. globiceps Clarke & Ruedemann. A very small somewhat distorted carapace of a Pterygotus may well represent this species.
Professor van Ingen has also succeeded in discovering still another eurypterid fauna southwest of the Delaware Water Gap, at the Swatara Gap, Lebanon co., Pa. The interesting feature of this fauna is that it occurs in association with marine fossils suggesting horizons lower than the Salina and corresponding to parts of the Niagaran, possibly as low as the Clinton.
Eurypterid remains were encountered in three beds distinguished as: 182 B 16h, 182 B 23 and 182 C 4x.
182 B 16h, an olive gray sandy shale, has furnished:
1 Small carapaces, belonging to species closely related or identical with Eurypterus maria, Hughmilleria shawangunk and Pterygotus globiceps
2 A patch of integument with finely preserved sculpture, identical with that ascribed here to Stylonurus sp. a and represented on plate 53, figures 10-12
3 Stylonurus cf. myops. Fragmentary medium sized carapace
4 Coxa, probably belonging to Hughmilleria
5 Small telson of an Erettopterus
182 B 23 has afforded a carapace showing the position of the eyes, and not distinguishable from Eurypterus maria. 182 C 4x contains:
1 Eurypterus maria. Large and small carapaces
2 Dolichopterus cf. otisius. Medium sized carapace
3 Stylonurus myops. Large and small carapaces
4 Hughmilleria shawangunk. Large carapace
5 Pterygotus cf. globiceps. Small carapace
6 Swimming leg of a Pterygotus or Hughmilleria
These faunules are so similar in their aspect and composition to that of the Shawangunk grit at Otisville, that, although they are too fragmentary for a conclusive identification, it seems proper to infer that they belong to the same or an approximate horizon. It is, therefore, of much interest that Professor van Ingen has in the Swatara Gap section obtained good evidence that these beds which also correspond to the Shawangunk grit in lithology and stratigraphy, contain marine fossils of much greater age than the Salina. Professor van Ingen states that B8x of his section carries an apparently Clinton fauna, and B19x a Rochester (or Lockport) fauna, while 182 C 4x contains Arthrophycus cf. harlani Conrad. It will be noticed that the fairly good Shawangunk grit fauna, cited from B16h, comes from an horizon between these beds.
Alternative hypotheses are suggested by this recent work; either that the Shawangunk grit is older than Salina age; or in view of the vast thickness of beds of like lithologic character in central Pennsylvania containing the eurypterid fauna of Otisville aspect, these rocks may represent a very long Upper Siluric time interval, of which a late stage only is represented by the thinner northern extension into the Shawangunk mountains. Here again, as in the fauna of the Normanskill and Schenectady beds, the eurypterids may have changed but very little through several geologic periods; and in all these cases cited, the Shawangunk grit, the Schenectady beds and the Normanskill beds at Kingston, there is identity in lithologic characters and indications of similar littoral conditions, of narrow gulf, or delta, or estuary.
AN ADDITIONAL SPECIES OF EUSARCUS FROM THE BASE OF THE SALINA FORMATION
After decades of industrious collecting of eurypterids from the New York Siluric waterlimes, the rich stores of these remains have not been exhausted. While this work was in press and partly in pages, Professor Gilbert van Ingen of Princeton University sent us some slabs from a loose concretion in Oriskany creek in Oneida county, N. Y., which carry three carapaces and other parts of an Eusarcus of very unexpected and peculiar character.
Eusarcus vaningeni nov.
See text figures 108-15
Description. The outline of the body is as in E. scorpionis.
Cephalothorax. The carapace is broadly subtriangular, about one third wider than long (not counting a frontal snoutlike prolongation), the two lateral margins converging at an angle of about 700 toward the anterior end which is produced into a linguiform process, about one fifth the length of the carapace. The base is to the lateral margin (excluding the snout) as 4:3. The posterior margin is distinctly bent forward in the middle and the postlateral angles are markedly truncate. The lateral margins are slightly concave in the posterior and as gently convex in the anterior half. The anterior process is one fourth as wide at its base as the basal margin of the carapace. Its lateral margins are nearly straight and converge slightly; the anterior margin is gently convex. The lateral and anterior margins are furnished with a filiform border, the posterior with a narrow doublure. The carapace culminates between or just posteriorly of the lateral eyes, a broad ridge extending thence backward toward the posterior margin. The lateral eyes were relatively small, only about one seventh the length of the carapace, submarginal, situated just posteriorly of the base of the tonguelike anterior process, apart about their length and about half their length distant from the lateral margin. The visual surface is as in E. scorpionis. The ocellar mound is very prominent and situated between the posterior extremities of the lateral eyes.
The appendages, so far as seen, are like those of E. scorpionis.
Abdomen. The tergites and sternites have the form and relative dimensions of those of E. scorpionis; of the postabdomen only one segment has been seen which indicates a tail as tubular and scorpionlike as in the genotype; and the telson has not been observed. The ornamentation is that of E. scorpionis, but the scales are smaller and more closely arranged.
Horizon and locality. The concretionary block which contained the remains of the three specimens was found loose at the foot of a high bank of Salina beds in Oriskany creek, near Farmers Mills, 3 miles south of Clinton, N. Y. The block is also full of lingulas and orbiculoideas by means of which its horizon in the bluff could be determined. It is there located about 21 feet below the base of the red Vernon shale in dark gray shales with intercalated waterlimes and dolomite beds. This shale formation has been considered by Mr Hartnagel as equivalent to the Pittsford shale, the lowest formation of the Salina beds in New York; or, as it combines the dark gray Pittsford shale with the typical Lockport dolomite, as the interlocking boundary of the Niagaran and Cayugan groups, or the closing stages of the Niagaran. However that may be, it is safe to consider this eurypterid horizon as situated at the base of the Salina beds, and either of Pittsford age or still older.
Remarks. E. vaningeni is in more than one way a very puzzling form. Its general features are undoubtedly like those of
Fig. 108-10 Eusarcus vaningeni nov. Fig. 108 Carapace, the frontal process bent downward. Holotype. Natural size. Fig. 109 A larger carapace showing the relatively broader frontal tongue, also bent downward. Cotype. Natural size. Fig. 110 Carapace and nearly complete preabdomen; the frontal process fully extended. Cotype. Natural size
Fig. 111-15 Eusarcus vaningeni nov. Fig. 111 Female operculum with portion of opercular appendage. Fig. 112 Seventh segment of swimming leg. Fig. 113 Postabdominal segment. Fig. 114 Ventral view of the appendages of carapace, I-IVe, the four pairs of endognathites or walking legs, showing the same relative lengths as in Eusarcus scorpionis, the second being the longest. c, coxa of swimming leg, with gnathobase; d, broad marginal doublure of carapace, not observed in other specimens of Eusarcus; m, portion of metastoma. Fig. 115 Sternite. All figures natural size
Eusarcus cicerops, an Otisville species, has these two features, the anterior process and the forward position of the ocelli, in common with E. vaningeni. The former, in the position of the lateral eyes and the broad base of the carapace, seems closely allied to E. vaningeni, and as our specimens of E. cicerops are all of early growth stages, it is possible that the mature specimens were still more like E. vaningeni. The presence of these two closely related aberrant types in the lowest Salina beds of Oneida county and in the Shawangunk shale, strengthens our inference as to the probable equivalence of the Shawangunk grit with the Pittsford shale. Eusarcus nasutus from the Frankfort beds at Schenectady and the still earlier Eusarcus linguatus from the Normanskill shale at Catskill also exhibit median extensions of the frontal margin of the carapace similar to the frontal lappet of E. vaningeni.
The compound eyes in E. vaningeni appear to be placed considerably farther inward than in E. scorpionis. We do not know, however, how much this difference is due to the fact that in E. vaningeni the entire carapace is spread out, having been rather flat along the lateral margin, while in E. scorpionis the marginal parts were more or less vertical and bent under, thus bringing the submarginal lateral eyes on the margin of the compressed specimen. This latter condition is seen in the types of plates 29 and 30.
NOTES ON ANTHRACONECTES
When investigating this genus we were unable to locate the types of the Pennsylvania Carbonic species described by C. E. Hall and James Hall. These have been found in the Hall collection of Chicago University, whence we were able to borrow them through the courtesy of Professor Stuart Weller. For the purposes of completeness and facility of reference some notes on the species are here given:
Eurypterus (Anthraconectes) mansfieldi C. E. Hall
Dolichopterus mansfieldi C. E. Hall. Am. Phil. Soc. Proc. Phila. 1877. 16: 621
Eurypterus mansfieldi James Hall. Sec. Pennsylvania Geol. Sur. PPP. 1884. p. 32, pl. 4, fig. 1–8; pl. 5, fig. 1–11; pl. 6, fig. 1; pl. 7, fig. 1; pl. 8, fig. 1–3
Eurypterus stylus James Hall. Ibid. p. 34, pl. 5, fig. 12–15
Cf. E. potens James Hall. Ibid. p. 37, pl. 4, fig. 9, 10
See text figures 43–47, page 220
E. mansfieldi and E. stylus are associated in the "shale immediately below the Darlington cannel coal, near Cannelton, Darlington township, Beaver county, Pennsylvania." Hall cites [op. cit. p. 35] as the distinguishing feature of E. stylus and E. mansfieldi that the former has a "shorter carapace, comparatively wider body, longer and stronger telson and the eyes are more oblique and distant." All these are differences due to compression. The specimens of E. mansfieldi are squeezed laterally, as shown by the longitudinal wrinkles, while those of the E. stylus are compressed longitudinally, as evinced by the transverse wrinkles [see Hall, pl. 5, fig. 15] and by the pushing together of the tergites. For the same reason the telson appears relatively longer in E. stylus than in E. mansfieldi. The types of both species have all other characters in common, even to the remarkable sculpture and the anterior median process of the carapace.
Fig 116, 117 Eurypterus (Anthraconectes) mansfieldi C. E. Hall. Fig. 116 One of the originals of E. stylus refigured to show the frontal spine and outline of carapace. × 2. (Hall, 1884, pl. 5, fig. 12) Fig. 117 A frontal spine. × 5 The frontal margin of the carapace bears a peculiar small, triangular lobe in the middle, which is well shown in the originals of Hall's figures, plate 5, figure 3, 12 and 15. In others it is broken out. In figure 12 it was clearly originally drawn in, but later erased again [see also our text fig. 44] and in his plate 6 it is still visible in outline. It is hollow, or spoonlike, on the upper side and has very strong walls.
The sculpture is beautifully preserved in the specimens, is of striking character and not exaggerated in the drawings. The scales of the carapace are broad and roundish in the middle part between the lateral eyes and become more angular and protruding at their posterior points as they approach the base of the carapace giving that part a shagreened aspect. The same feature is still more emphasized on the tergites and postabdominal segments. On these the anterior half is ornamented with extremely small, crowded, broad scales, which abruptly are replaced by the posterior zone of large pointed scales and imbricating larger and smaller ones. In the middle line a number of scales unite and rise into nodes, the scales themselves thickening into bulblike bodies [see Hall, pl. 5, fig. 3; pl. 8, fig. 1 and our text fig. 44]. The character of the scales is entirely that of A. mazonensis, the type of the subgenus [see pl. 26, fig. 1] and the median nodes are also found there. As we have already intimated these features are phylogerontic characters which are more fully developed in British Carbonic forms.
In the same class of phylogerontic characters belong the exaggerated development of the postlateral angles of the epimera of the tergites and postabdominal segments into thick, striated falcate spines [see text fig. 44]. In many specimens they seem to be absent [text fig. 43]. This is entirely due to the brittle nature of these defensive organs which easily broke away and are frequently found detached.
A similar explanation may be offered for the apparent spineless character of the legs [see text fig. 43], for in reality the spines are much stronger and thicker than in most earlier eurypterids; and also mostly broken away in the specimens. They were also strongly striated [see text fig. 46].
The same phylogerontic tendency to spinosity is also shown in the development of the distal fringes of the leg joints into spines [text fig. 46] and of the posterior margins of the tergites and the fringe of rather long teeth developed on the outside of the palette of the swimming leg [see text fig. 43]. Finally the extreme length and slenderness of the telsonspine is also a character pointing to the same condition.
Two large fragments which Hall supposed to be those of ectognaths were figured and, in the explanations of his plates, referred to a new species, E. potens. One is apparently a gnathobase and the other a portion of a sternite. Both indicate specimens of a size much larger than the types of E. mansfieldi with which they are associated, but as they exhibit an ornamentation quite as in that species, it is quite probable that E. mansfieldi grew to corresponding proportions.
Eurypterus pennsylvanicus C. E. Hall
E. pennsylvanicus C. E. Hall. Am. Phil. Soc. Proc. 1877. 7: 621
E. pennsylvanicus James Hall. Sec. Pennsylvania Geol. Sur. Rep't of Progress, PPP. 1884. p. 31, pl. 5, fig. 18
This species was based on a single small carapace, very similar in its characters to that of E. mansfieldi but markedly shorter (length to width as 3 : 5), and coming from an arenaceous Carbonic shale at the Rooker farm, Pithole City, Venango co., Pa. The outline is quite regularly semicircular; the posterior parts of the lateral margins slightly concave and the postlateral angles slightly produced but not into distinct mucros as in the original figure. The eyes are small (between one fourth and one fifth the length), the nodes prominent. They are separated by a distance about one half the breadth of the carapace. As in other specimens from sandy beds, the glabellalike ridge of the middle of the carapace is well preserved between the eyes and bears a distinct circular ocellar mound just back of the lateral eyes. This species is probably closely allied to E. mansfieldi.
HUGHMILLERIA: VENTRAL SURFACE OF THE CEPHALOTHORAX
The chance exposure of the lower side of the cephalothorax in this genus has brought out a structure which none of the material before examined has displayed and an illustration of the details of this structure is
Text fig. 118 Hughmilleria pittsfordensis Sarle. Shows marginal plates of ventral surface of carapace. e, epistoma; as, attachment scars of chelicerae; als, antelateral shield; ms, marginal shield; le, impression of the lateral eye; pd, posterior doublure. × 4/3 here given. In the anterior median position lies a relatively long plate resembling an inverted lyre, which is identical with the object described by Sarle and reproduced elsewhere by ourselves as the supposed "metastoma of Dolichopterus??" It is the epistoma. It is bounded by sharp sutures on the lateral margins and terminates with its bilobate portion in front of the mouth. On its posterior lobes are two sharply outlined circular scars indicating either the attachment of muscles or more probably the bases of the chelicerae. This epistoma is flanked by two semielliptic plates, the antelateral shields, which in their turn are separated by distinct sutures from the marginal shields at the sides. The latter show a clavate widening at their posterior ends. The narrow posterior doublure, which is not connected with the marginal shield, completes the system of marginal plates on the ventral side of the cephalothorax which hold the appendages and membranes in place.
A comparison of the structure here described with that of Pterygotus shows that the epistomas of both genera agree in general form. That of Hughmilleria is, however, the longer and more slender, an adaptation to the more elongate form of the head shield in that genus, and there are in Pterygotus no antelateral shields separated by sutures from the marginal shield.
The epistoma exists, so far as we now know, in no other genera than Hughmilleria and Pterygotus; that is, in the two genera which are characterized by a very strong development of the chelicerae, and this fact indicates that the plate itself has resulted from strains originating from these strong and active arms.
NOTE ON PTERYGOTUS COBBI var. JUVENIS nov.
See text figures 119-21
In the description of P. cobbi, in the body of this memoir, we had only two free rami of the pincers at our disposal, all that was known of the species. A large collection of eurypterid material since obtained by Mr Hartnagel in Herkimer county, contains two small specimens of Pterygotus on the same slab, one of which possesses the characteristic pincer of P. cobbi with some slight differences, of such nature as to be quite probably ascribable to an earlier growth stage of the species. We therefore refer to these specimens as P. cobbi var. juvenis.
These two specimens differ in a number of characters from both the common P. buffaloensis of the Bertie waterlime at Buffalo and the P. macrophthalmus of Herkimer county.
Fig. 119 Pterygotus cobbi var. juvenis nov. Pincers. × 3 The most important of these differences rests in the pincers which are rounded in front as in P. cobbi and the free ramus of which shows the denticles of the type of that species but is stouter and distinctly higher in the middle. The carapace is more evenly rounded anteriorly than in the other two species here cited and especially longer (length to width as 4 : 5); the compound eyes are relatively larger while the abdomen appears slightly broader and stouter (the preabdomen is 26 mm long and 19 mm wide); and the telson is in both specimens narrower than in P. macrophthalmus, a difference which is surely in part and perhaps wholly due to preservation, the thin telsons being somewhat laterally compressed.
On account of the scarcity of the material we do not know to what extent these differences are expressions of different growth stages, but it is quite obvious that P. cobbi as represented by these specimens, was remarkably similar in all its features, save the pincers, to P. buffaloensis and P. macrophthalmus.
Judging from the fragmentary pincers of the specimen figured by Pohlman [1883, pl. 3, fig. 3] as P. buffaloensis, we surmise that this also belongs to P. cobbi.
Horizon and locality. Bertie waterlime, Schooley's farm, Litchfield, Herkimer co., N. Y.
Fig. 120-21 Pterygotus cobbi var. juvenis nov. Fig. 120 Dorsal aspect. Fig. 121 Ventral aspect. Both somewhat laterally compressed. Natural size
GEOLOGIC DISTRIBUTION OF NORTH AMERICAN SPECIES OF EURYPTERIDS AT PRESENT KNOWN
a The Schenectady beds have been termed in this work the Schenectady facics of the Frankfort beds. They are now referred to the upper Trenton as a distinct unit [see p. 411.]
- In a quite recent paper (Smithsonian Miscellaneous Collections. Middle Cambrian Merostomata, April 8, 1911) Dr Walcott has given figures of additional specimens referred to Beltina danai, from new horizons regarded as Algonkian, the Altyn limestone, near Altyn, Montana, and a silicious rock in Alberta, Canada. These retain a certain degree of convexity and show a defined merostome sculpture [pl. 7, fig. 2–4], while figures 3 and 4 give clear outlines of merostome segments. It is not quite clear on what basis of structure these very evident merostome remains are identified with the Greyson shale examples of "Beltina" though they intimate the extremely ancient age of the Merostomata and their extraordinary specialization in the earliest fossiliferous rock beds.
- Against this again it is asserted by Fritsch [1904, p. 64] that the specimen exposes the dorsal side and that only some of the ventral organs are pressed through the mutilated carapace and that it hence could not show stigmata.
- Thorell [op. cit. p. 22] cites for comparison the single known recent scorpion which is destitute of eyes, namely, Belisarius xambeui.
- C. D. Walcott. Middle Cambrian Merostomata. Smithsonian Miscellaneous Collections. 1911. v. 57, no 2. p. 15.
- In the body of this work the species from the Schenectady beds have been referred to the "Schenectady facies" of the Frankfort beds. Investigations since carried on by the junior author in the thick formation of sandstones and shales in the lower Mohawk valley, hitherto referred by all authors to either the Hudson River shale or the Frankfort beds, have shown that the faunal differences which induced us to distinguish the beds as Schenectady facies are of such nature that the whole formation has to be placed within the middle and upper Trenton. It will therefore in a forthcoming bulletin be distinguished as the Schenectady formation.
- More or less shapeless patches of these seaweeds and possibly also of eurypterid integument from the Normanskill shale at Kenwood near Albany were described by R. P. Whitfield [Am. Mus. Nat. Hist. Bul., v. 1, no. 8, 1886, p. 346, pl. 35] as Rhombodictyon and referred to the sponges on account of an apparent spongelike fibrous structure consisting, according to Whitfield, of two or three sets of rods, the principal ones of which are "straight, rigid and apparently cylindrical." This peculiar structure is shown by all the thicker specimens from the shale of the Broom street quarry and is there obviously only a system of parallel shrinkage or cleavage cracks found wherever the carbonaceous films become rather thick; and is entirely independent of outlines of the fossil but strictly parallel on all fossils of the same slab, thereby indicating its connection with a latent cleavage of the folded beds. The parallel main cracks are connected by more irregular cross cracks, the whole forming a very deceptive pattern. Sometimes these cracks have become secondarily filled by calcite or pyrite and the carbonaceous matter subsequently destroyed, whereby an apparent spongelike system of rods has resulted. Inspection of Whitfield's types in the American Museum of Natural History has shown that the types of the two species of Rhombodictyon are of quite the same nature as the thick carbonaceous patches of seaweeds from the shale at Catskill.
- The fact that this process is more or less bent downward in two of the specimens might lead to the assumption that it is homologous to the epistoma of Pterygotus and might have been bent under entirely. Several considerations disprove this assumption, namely, the absence of a suture separating it from the anterior part of the carapace and the passing of the filiform thickened border around the process; and above all, the existence of another species of Eusarcus (E. cicerops) with a similar but much less developed anterior process [see pl. 36, fig. 3, 4] which is clearly a straight extension of the carapace.
- Allegheny formation of the Pennsylvanian.