THE EURYPTERIDA OF NEW YORK. 227 
legs are in the same number as in Eurypterus. The swimming feet appear 
to differ by the straighter, less rounded outer margins. In the specimen 
the rhomboidal plates are not given. From the impressions of the joints 
of the swimming feet their relative dimension does not seem to accord with 
Eurypterus. The four pair of anterior feet proceed from two elongate 
oral plates of which the impression is very distinct. The spines of the 
anterior feet appear to be long, curved, and to have an anterior direction. 
The absence of chelate appendages to the posterior margin of the feet is 
particularly noticeable. The first seven broad segments of the abdomen 
form a large ellipse. There is an evident and remarkable narrowing of the 
succeeding caudal segments. Of these six appear to be made out on 
the specimen. The surface of the cast is punctate with scattered tri- 
angular impressions. The cast shows a widening of the terminal segment 
and no traces of a spiniform process are exhibited.' 
Of the differentials indicated in the passage quoted, the following 
] 
have stood the test of larger collections: the much “‘ narrower ”’ cephalo- 
thoracic portion, the broad large ellipse of the abdomen and the ‘‘ remarkable 
narrowing ’’ of the postabdomen (‘‘ caudal segments’’). At least three, 
possibly four species, exhibiting quite similar characters of general form, 
are known from the British Siluric rocks and these have been referred 
to Eurypterus by Woodward, the differences in outline not being con- 
sidered of generic importance by that eminent authority. It is not sur- 
prising therefore that authors generally have shown little inclination to 
‘recognize this genus Eusarcus. | 
Grote’s successor as curator of the Buffalo Society’s museum, Mr 
Pohlman, was apparently the first to assail the proposed genus, stating 
[1886, p. 29] that the discovery of several new specimens had shown that 
the form has “the leading characteristics of the genus [Eurypterus], as 
given by DeKay,” viz, “a terminal joint prolonged into a sublinear or 
lanceolate triangular spine with serrated edges,’ and ‘‘ eyes reniform or 
oval, placed within the margin of the carapace.’ Pohlman’s observations 
in regard to the telson, which is as in Eurypterus, are correct, but the 
original of the supposed carapace of Eusarcus which he figures [op. cat. 
'In the original description the specimen is erroneously described as presenting a 
ventral surface. 
