448 



NORTH AMERICAN INDEX FOSSILS. 



230. A. textilis var. arenaria Hall. Devonic. 

 Distinguished from A. textilis by its greater size and its shorter 



posterior wing which extends only about one half the distance 

 from beak to base. 



Very common in the Oriskany of New York, New Jersey, 

 Pennsylvania, Maryland, Ontario, Quebec. 



231. A. muricata Hall. (Fig. 591, a.) Devonic. 



Fig. 591. a, Actinopteria muricata, X 2 \ b, A. subdecussata ; c, A. decussata, left 

 valves ; d, Ptychopteria sinuosa, left valve, showing oblique cardinal and lateral teeth ; 

 e, f, P. sao, left and cardinal views. (Pal. N. Y., V.) 



Small. Beak acute and arching over the hinge. Anterior ear 

 separated from the body of the shell by a broad undefined furrow 

 which is bounded anteriorly by a strong fold. Surface marked 

 with 8—12 strong rays alternating with finer ones which are con- 

 tinued over the posterior ear. Rays crossed by concentric striae. 



Marcellus : New York, Pennsylvania. 



