66 PALEONTOLOGY OF NEW YORK. 



spines. The radii are less conspicuous on the ears, which also show a few 

 concentric undulations. 



Internal characters not preserved. The ligamental area appears as a 

 simple fold in the hinge. 



The specimen has a length of 15 mm. ; height 13.5 mm. ; hinge-line 

 18 mm. 



This species has the general form and aspect of P. Hermes and P. Icetus, but 

 is proportionally wider, with different and characteristic surface markings. 



Formation and locality. In soft shales of the upper part of the Hamilton 

 group, shore of Canandaigua lake, Ontario county, N. Y. 



Pterinopecten conspectus. 



PLATE XVII, FIGS. 17, 18, 20, H. 



Pterinopecten conspectus, Hall. Pal. N. Y., vol. v, \<t. 1. Plates and Explanations: PI. 17, figrs. 17-21. 



Jan.. 1SS3. 



Shell of medium size, sub-rhomboidal ; moderately old i que in young shells, 

 scarcely oblique in older ones ; length and height about equal, the length 

 usually a little greater ; pallial margins regularly rounded, straighter poste- 

 riorly, and merging into the ear without definite limitation. 



Left valve moderately convex. Right valve nearly flat, narrower and 

 oblique, with a deeper byssal sinus. 



Hinge-line straight, nearly central, equalling, or a little greater than, the 

 length of the shell. 



Beak sub-acute, anterior to the centre of the hinge-line, directed slightly 

 forward. Umbonal region somewhat prominent, subtending an angle ■ of 

 about 75°. 



Ears triangular. Posterior one much the larger, not distinctly defined on 

 the valve ; margin slightly concave ; extremity rectangular or somewhat 

 acute. Anterior ear small, distinctly defined by a rounded sulcus ; margin 

 convex; extremity rounded or sub-angular. Byssal sinus moderate in the 



