4IO NORTH AMERICAN INDEX FOSSILS. 



21. E. grandis Grote and Pitt. Siluric. 

 Large, attaining a length of two or three feet; posterior abdomi- 

 nal segments subcylindric. 



Waterlime at North Buffalo, New York. 



22. E. scorpionis Grote and Pitt. Siluric. 

 Smaller than E. grandis; average length about one foot ; appear- 

 ance strikingly like that of a scorpion ; telson strongly curved. 



Waterlime at North Buffalo, New York. 



X. DOLICHOPTERUS Hall. 

 Differs from Eurypterus in having the swimming legs with elon- 

 gate joints, the seventh and eighth joints little dilated; but the 

 terminal piece or palette, extremely developed ; postoral plate lyrate 

 or cardiform-lyrate; central thoracic appendage strong, thick and 



Fig. 1711. Dolichopterus macrocheirus^ a specimen with posterior portion incomplete 

 and some appendages missing, X Yz' (Pal. N. Y., III.) 



simple in its posterior part. (This and the preceding feature are 

 shown only in ventral aspect.) Siluric. 



23. D. macrocheirus Hall. (Fig. 1711.) Siluric. 



Large ; cephalothorax subquadrangular with nearly parallel sides. 



