THE EURYPTERIDA OF NEW YORK 233 
of the carapace. The position of the longer row of spines, however, will 
determine the side on which the walking legs come to rest when lmply 
sinking to the bottom. 
The difference in the walking legs finds its strongest expression in 
the fourth pair. In Eurypterus the fourth is not only longer and thinner 
than the others, but also lacks the spines, while in Eusarcus, it is the 
shortest leg of the last three pairs, though equally strong and, like the 
others, provided with spines on all segments. 
Another difference consists in the form of the swimming legs. Cor- 
responding to the plumper, heavier form of Eusarcus, these legs are more 
powerfully developed. The paddles are much longer and broader, while 
the preceding segments, connecting with the coxae, are much shortened and 
thickened, so that the eighth segment in Eusarcus is fully as long or even 
longer (in old individuals) than the 2-6 segments together. The latter 
segments are consequently, in their proportions and even in their form, 
entirely different from those of Eurypterus. In these characters the swim- 
ming leg of Eusarcus has become closely like that of larger species of 
Pterygotus suchas P. buffaloensis. 
Eusarcus scorpionis Grote & Pitt 
Plates 27-34; plate 35, figures 2-5; plate 36, figure 1 
Eusarcus scorpionis Grote & Pitt. Buffalo Soc. Nat. Sci. Bul. 1875. 3:1, 
pl. 1 
Eusarcus grandis Grote & Pitt. Ibid. p.17 
Eusarcus scorpionis Pohlman. Jbid. 1881. 4: 21 
Eurypterus scorpionis Semper. Beitr. z. Pal. u. Geol. Oesterr.-Ung. u. d. 
Orients. 1898. 11: 86 et seq. 
Eurypterus scorpionis Seeman. zd. 1906. 19:57 
Not Eurypterus scorpionis Pohlman. op. cit. 1886. 5: 29-30, pl. 3, 
fig. 3 
Our description of this hitherto very imperfectly known species is 
based on the remains of 20 specimens, apparently all that have been thus 
far secured. Seven of these are entire, or nearly entire, specimens and one 
