228 NEW YORK STATE MUSEUM 
pl. 3, fig. 3] and which is now in the collection of Columbia University, 
proves to be a carapace of Dolichopterus siluriceps [pl. 26, 
fig. 3], im which the eyes are normally intramarginal. We have however 
specimens of Eusarcus scorpionis which leave no doubt of the 
marginal position of the eyes in that species, and thus afford an import- 
ant differential of the genus. In none of the British species with typi- 
cally Eusarcuslike outlines (viz, Eurypterus scorpioides and: 
E. punctatus) was the position of the eyes known to Woodward, and 
one species, of which only the triangular carapace and subcircular abdo- 
men have been found, was referred by him to Pterygotus (P. rani- 
ceps) on the strength of its marginal eyes. | 
Grote and Pitt based their new genus on mere differences in outline 
and though Woodward did not regard these as generic characters, and 
Miller [N. A. Geol. & Pal. 1889, p. 548], obviously for like reasons, refused 
to recognize the genus, while Zittel cites it as doubtful, it is entirely evident 
from our present knowledge that the group, typically represented by 
Eusarcus scorpionis, is generically distinct from all its allies. 
On this continent there is another locality, Kokomo, Indiana, which 
has afforded representatives of Eusarcus sometimes in gigantic examples. 
The first specimens were described by Claypole as Eurysoma new- 
lini [1890, p. 259]. The term Eurysoma was soon after withdrawn by 
its author as preoccupied and was replaced by Carcinosoma. In 1894 
another species (C. ingens) from the same locality was added 
and Eusarcus indicated as the nearest ally of the new genus, with 
the following qualification: ‘‘ But the description of that genus |[Eusarcus] 
mentions that the cephalothoracic portion is considerably narrower than 
in allied forms and that the terminal segment shows a widening and no 
trace of spiniform process. There are also several other minor points of 
difference.”” None of the differences here suggested by Claypole really 
exist, for our working material, which probably comprises nearly all Kokomo 
specimens ever collected, shows this carapace to have quite the same sub- 
triangular form as in the Buffalo specimens, while both possess an ensiform 
