Dolichopterus siluriceps[1] nov.
Plate 26, figure 3
Eusarcus scorpionis Pohlman. Buffalo Soc. Nat. Sci. Bul. 1886. v. 5, no. 1. p. 30, pl. 3, fig. 3
Description. In 1886, as above cited, Pohlman figured and described as belonging to Eusarcus scorpionis, a carapace that subsequently came into the possession of Prof. J. S. Newberry and this specimen is now in the museum of Columbia University (no. 3078).
Eusarcus scorpionis has a subtriangular carapace and it is apparent that this specimen, both in outline and the position of the eyes, belongs to Dolichopterus; at the same time it differs in its proportions specifically from the genotype D. macrochirus. In the carapace of the former the proportion of length and width is as 6 : 7, but here it is as 6 : 8.5, as a result of which the carapace of D. macrochirus looks squarish in outline, while this is broadly quadrangular. The relation of these carapaces is similar to those of Eurypterus remipes and E. lacustris. A further obvious difference consists in the marked contraction of the carapace in the anterior half and the resulting strongly converging anterior lateral margins in E. siluriceps.
The carapace of this species furnishes the following description:
Hexagonal, basal side the longest, curving broadly forward in the middle third; the lateral margins are very slightly divergent behind and more strongly convergent in front; the greatest width of the carapace being at the point of change of direction in the lateral margins. The postlateral angles are nearly right angles, very slightly rounding, while the very obtuse antelateral angles are broadly rounded, and are connected in front by a nearly straight or slightly concave anterior margin. The eye tumescences are broken out. Their cavities occupy nearly one
- ↑ Silurus a catfish; in allusion to the form of the carapace.
