PELECYPODA—PRIONODESMACEA. 



425 



169. L. rafinesquii Hall. (Fig. 555, c.) Devonic. 

 Anterior ear broadly arched. Surface covered with concentric 



striae which at intervals are raised into strong lamellae and undula- 

 tions. 



Hamilton : New York, Ontario. Lower Devonic of Nevada. 



170. L. dekayi Hall. (Fig. 555, d.) Devonic. 

 Differs from L. Iczvis in its larger size and more defined posterior 



cardinal slope ; from L. rafinesquii in its finer and not lamellose 

 striae though concentric undulations are at times present. 

 Characteristic of the Hamilton of New York. 



FlG. 555. a, b, Leiopteria Icevis, right and left valves, X2; c, L. rafinesquii; d, 

 L. dekayi; <?, L. chemungensis. (Pal. N. Y., V.) 



171. L. chemungensis Vanuxem. (Fig. 555, e.) Devonic. 



Differs from L. dekayi in its longer hinge line, larger posterior 

 ear, more acute beak, and narrower body of shell. 



Chemung of New York, etc. 



XLIX. Leptodesma Hall. 

 Differs from Leiopteria in its acute instead of rounded anterior 

 ear ; lateral tooth single and nearly parallel to hinge line. 



Devonic. 



