22 



such enlargement, but ends in a gradually tapering broken tail joint, 

 which corresponds with the spine of Eurypterus when broken off 

 near the beginning of its triangular portion. 



In spite of all efforts made I have not been able to obtain any 

 specimen of Eusarcus which would help to settle this question defi- 

 nitely; the species appears to have been as rare as Pterygotus, for 

 only two specimens have hitherto been found, both of which are in 

 the museum. 



The cuts for this paper have been made and presented by Mr. 

 Henry Chandler, of this city. 



