24.", 



rays, with smaller intermediate ones on the left valve; con- 

 centric striae; and a few obsolete rays on the right valve. 



Found in the Stictopora and Demissa beds ( rather com- 

 mon); in the shale, down to twelve feet below the En- 

 crinal limestone, at Sections 6 and 7 (rare); in the shale 

 below the Nautilus bed, in Avery's Creek (rare); and at 

 "Hamburg and elsewhere on Lake Erie Shore/' (Hall.) 



Gents ACTINOPTERIA. Hall. 



[Ety. : Aktin, a ray ; pteron, wing.] 

 (1884 : Pal. N. Y., Vol. V., Pt. I., p. xii.) 



"Characterized from Pterinea in the absence of a broad, 

 striated ligamental area, and strong cardinal and lateral 

 teeth. Right valve snb-convex ; surface with fine rays." 



Fig. 160. Actinopteria decussata. Left valve, showing the strongly decussated radii 

 right valve not preserving the radii (from Hall). 



