straight; slightly bulging in the posterior half; posterior margin broadly concave. Antelateral angles very prominent, a little larger than a right angle; genal angles well rounded in the type, rectangular in other specimens. A distinct flat or beveled border follows the lateral margin, and a narrower one the frontal margin. The lateral eyes are situated at the antelateral corners, relatively small (about one fifth the length of the carapace), semicircular to semielliptical in form, the straight diameter forming the inner margin. The visual surface was apparently crescentshaped. The ocelli were situated on a line with the posterior extremities of the lateral eyes. The ornamentation [see pl. 83, fig. 10] consists of closely arranged, low flat nodes.
Horizon and localities. Frankfort shale at Schenectady (Dettbarn quarry), Aqueduct, Rotterdam Junction and Duanesburg, whence the type and some of the best specimens came.
Remarks. We have about a dozen carapaces, mostly from Schenectady, which agree in general outline and position of the lateral eyes, but show slight variations in the character of the frontal margin which in some exhibits a rather sharply protuding middle projection while in others it is somewhat emarginate. It is, however, quite probable that these latter variations from the form of the frontal margin of the type, are due to lateral and oblique compression and folding of the thin integuments.
This species must have attained considerable size, for one carapace [pl. 83, fig. 14] was about 69 mm long and 62 mm wide at the frontal angles. The type specimen measures 8 mm by 8 mm.
A metastoma has been found which recalls that of D. macrochirus.
Dolichopterus latifrons nov.
Plate 83, figures 15–16
Description. Carapace of small size, spade-shaped in outline, broader by one half in front than at the base, its greatest width equal to its length; the frontal margin marked by a flat or beveled border, most produced in the middle, and posteriorly bounded by a straight transverse projecting
