424 NORTH AMERICAN INDEX FOSSILS. 



Fig. 553. a, b, Actinodesma erectum , right and left valves; c, A. occidentale ; d, Lim- 

 optera macroptera ; e, L. obsoleta. All figures, X \- (Pal. N. Y., V.) 



XLVIII. Leiopteria Hall. 

 Outline P/eriuea-like. Ligament area longitudinally striated. 

 One or two oblique lateral teeth present. Cavity of beak partially 

 separated from the anterior end by a short partition. Surface 



without rays. Siluric-Mississippic. 



167. L.? subplana (Hall). (Fig. 554.) 



Siluric. 



Depressed-convex. Right and left 

 valves similar. Ears poorly defined. 



Rochester and Cobleskill of New 

 York. Guelph : New York, Canada. 



168. L. laevis Hall. (Fig. 555, a, b.) 



Devonic. 



Length and height nearly equal. 

 Anterior ear marked by a strong, an- 

 gular fold. Surface covered with ob- 

 scure traces of radiating striae. 

 ttt~ „. t • j.* • a l±i Marcellus and Hamilton: New York, 



Fig. 554. Leiopteria? subplana, ' 



left valves. (Pal. N. Y., II.) Pennsylvania. 



