THE EURYPTERIDA OF NEW YORK 273 
Dolichopterus siluriceps' nov. 
Plate 26, figure 3 
Eusarcus scorpionis Pohlman. Buffalo Soc. Nat. Sci. Bul. 1886. v. 5, 
no, tI. op. 30, pl. 3, fig. 3 
Description. In 1886, as above cited, Pohlman figured and described 
as belonging to Eusarcus scorpionis, a carapace that subse- 
quently came into the possession of Prof. J. S. Newberry and this speci- 
men is now in the museum of Columbia University (no. 3078). 
EHEusarcus 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 propor- 
tions 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. macro- 
chirus 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 con- 
sists 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 con- 
nected in front by a nearly straight or slightly concave anterior margin. 
The eye tumescences are broken out. Their cavities occupy nearly one 
1Silurus a catfish; in allusion to the form of the carapace. 
