98 



TRANSACTIONS OF THE 



Eurypterus lacustris, Harlan. 



By this name we intend to designate a well marked 

 fossil species of this genus from the shore of Lake Erie, 

 Penna. The specimen is preserved in the Museum at 

 Buffalo, N. York; where we had an opportunity of in- 

 specting it, and of making a drawing, in the autumn 

 of 1829. 



The following are the comparative dimensions of the 

 two species. 



E. lucustris E. remises 



Total Length, 5 inches 3J inches 



Length of the head l\ " 1 " 



Breadth 2\ " 1^ 



Breadth of the body 2| " If " , 



Distance between eyes 1 " Of " 



but other differences exist beside those of size and pro- 

 portions. The transverse bands or joints are propor- 

 tionably wider in the lacusiris, consequently there are 

 fewer of them in a given space. These bands are 

 nearly equal in the remipes, those of the former on the 

 contrary are broadest above, and narrower near the 

 tail — the first plate, nearest the head being double the 

 size of the others. The tail in the remipes was want- 

 ing in the specimen — a faint outline of this member 

 existed in our specimen, in which it appears to have 

 been depressed and expanded, but contracted above 

 where it unites with the body. 



Some portions of the present species are more per- 

 fectly preserved than in the remipes, from which it ap- 

 pears that all the feet consist of five articulations, of 



