THE EURYPTERIDA OF NEW YORK 229 
telson. There are only minor differences between the Buffalo and Kokomo 
specimens; the latter are undoubtedly congeneric and the term Carcinosoma 
has to yield to Eusarcus. 
From the study of the large collection of material representing the 
genotype we consider the genus as characterized by (1) the triangular 
carapace, (2) the marginal and forward position of the eyes, (3) the decrease 
in length of the walking legs backward, (4) the spinosity of all walking 
legs, (5) the broad elliptic to subcircular preabdomen, (6) the sharply 
defined, greatly lengthened, cylindrical postabdomen, (7) the broad and 
short, subtriangular metastoma, (8) the distinctive proportions of the 
segments of the swimming legs. 
These characters, we believe, are correlated and shared by a number 
of species which thus constitute a well defined group. We have been able 
to satisfy ourselves as to their presence in Carcinosoma newlini 
Claypole (including C. ingens Claypole), save the form of the metas- 
toma which has not been clearly seen. Woodward’s elaborate description and 
excellent figures of Eurypterus scorpioides bring out all of 
these characters save the position of the eyes which were not observed. 
The inversely triangular form of the metastoma is particularly well 
established in that species. A like shield-shaped metastoma is assigned by 
Woodward to Eurypterus punctatus, known only by disjointed 
parts and regarded by him as closely related to E. scorpioides. 
Hurypterus obesus H. Woodward may be the young of 
E.scorpioides, a possibility suggested by the author of the species; 
at any rate, it strikingly exhibits the characters of Eusarcus, the last 
drawing published [1872, pl. 30, fig. 8] also showing the characteristic 
triangular carapace thus leaving only the supposed intramarginal eyes 
as a discordant feature to which we will return in another chapter. 
The Pterygotus raniceps H. Woodward,, referred by its 
author to that genus on account of its marginal eyes, leaves no doubt 
in our mind as to the propriety of its reference to Eusarcus, on account 
of the triangular form of its carapace, the forward and marginal position 
