The body plate in this group is very narrow (76 mm) as compared to its length (23 mm). Its division into right and left halves by a suture, the arching of each half and the produced antelateral angles indicate it to have been a paired sternite.
In the second group one of the imperfect arms consists of the four distal joints, the other of two imperfect proximal joints. The joints of the former are short and expanded at the articulations. The first and second are each provided on the posterior side with a pair of distally directed spines. These are long, curved and sharp like those of the large arm of the other group. The second has also, on the opposite side of the distal angle, a single, large one extending parallel with the axis of the arm. The penultimate is long and shows no sign of having been spiniferous. The terminal is about equal in length to the spines and, like the terminal appendage in the other group, is clawlike. This arm, judging from the shortness of the joints and the broadening at the articulations, probably corresponds to the second described from the other group. The joints of the other arm appear to correspond to part of joints two and three of the first of that group.
Associated with this last, and lying partially beneath its larger end, is a fragment of test which is ornamented by sharp, triangular scales differing from anything found on the other eurypterids herein described. However, it is not certain that this had any connection with this arm. Aside from this possibility, neither the appendages nor the sternite show any signs of ornamentation.
The most noticeable features revealed by these specimens are: the robustness and the great difference in size of the several pairs of endognathites; on the anterior three of these the arrangement in pairs of the posterior spines, which, on the first two, are noticeable for their shortness and lanceolate form, and on the third for their length and curvature; the high degree of specialization of the fourth pair of endognathites, shown by the great length of the joints and the number and large size of the spines; the narrowness and proportionately great length of the compound sternite; and the probability of there being several compound sternites. It is evident that the animal had a long, slender body with long, very strong limbs.
From a comparison of these parts with those of the various genera of eurypterids, it appears that they do not agree very closely with any. To show this, it is necessary only to point out certain of the more evident differences. In Eurypterus proper the fourth endognathite, to which I consider the longer of these arms to correspond, consists of nine joints, probably a greater number than is possessed by the other; besides, it bears no spines except the two formed by the prolongation of the eighth or penultimate joint. On the three anterior pairs of endognathites the spines are more uniform in shape and size. The body is proportionately broader
