LAMELLIBRANCHIATA. 57 



The dimensions of the right valve described are as follows : height 43 mm., 

 longitudinal diameter 42 mm., and hinge-line apparently about 25 mm. 



This species differs from L. Pobjdorus by its circular outline, convexity, obtuse 

 beak, ample umbo and surface characters. _ It difters from L. magnificus and 

 L. macrodontus in the greater convexity of the valve and fullness of the umbo, 

 as well as in the character of the rays. It is also much smaller than those 

 species. 



Formation and locality. In a fine semi-calcareous, argillaceous sandstone 

 (lying above the conglomerate ?) of the Upper Chemung group, near Panama, 

 Chautauqua county, N. Y. 



PTERINOPECTEN, Hall. 



Pterinopecten multiradiatus. 



PLATE I, FIGS, (i, 7. 



Pterhidpecteii iimltiradiatu,<i, Hall. Pal. N. Y., vol. v, jit. 1. Plates and Explanalioii.s : PI. 1, hgs. 6, 7. 



■Jan., 1888. 



Shell large, rhomboidal, body of the valve longitudinally obovate ; length and 

 height nearly as five to four ; anterior and basal margins regularly curved, 

 the postero-basal margin produced and the body of the shell extending 

 thence in a direct line to the beak. 



Left valve moderately and regularly convex. Right valve unknown. 



Hinge-line straight, anterior, less than the length of the shell. 



Beak obtuse, rounded, directed forward, slightly rising above the hinge. 

 Umbonal region ample, subtending an angle of about 105°. 



Ears triangular, flat, moderately well-defined ; margins slightly concave ; 

 extremities rectangular. Posterior ear about twice the size of the anterior, 

 limited by a stronger ray and the abrupt post-cardinal slope of the valve. 

 The anterior ear is limited by a distinct but undefined sulcus. Byssal sinus 

 scarcely marked. 

 8 



