4o6 



NORTH AMERICAN INDEX FOSSILS. 



cleft ; legs progressively increasing in length backward, the anterior 

 pair small with pincers or chelae ; second, third and fourth pairs six- 

 to seven- jointed, and covered with fine spines; fifth pair eight- 

 jointed; posterior (sixth) pair consisting of eight segments, large 

 and powerful, with a large, subquadrate basal joint in each and a 

 broad terminal '' paddle." Anterior six segments of abdomen occu- 



K 



Fig. 1706. Euryptertts pitisforde^isis, ante- 

 rior portion of a specimen, X Yi- (After Fig. 

 Sarle. ) 



1707. Eurypterus eriensis. 

 (After Whitfield.) 



pying together about one fourth of the entire body length ; they are 

 short, broad and of nearly uniform shape; the succeeding segments 

 are ring-like, and progressively decrease in diameter, thus causing a 

 tapering of the body; telson long and slender. Siluric-Permic. 



12. E. maria Clarke (Figs. 1705, a-c\ 1713, d, e.) Siluric. 



Small ; with large, crescentic eyes ; abdomen very little expanded ; 

 young strongly contracted in lower part of abdomen. 



Shawangunk conglomerate (black shale layers) of New York. 



