04 PALEONTOLOGY OF NEW YORK. 



wrinkled fntiii the apex to below the middle of the vulve. The surface 

 iiiiirkings are finer and sub-e(iual over the posterior ear. A small sjiace on 

 the umbo, as in Aviculopeden bellus, is destitute of radii. 

 Internal characters not known. 



This species dillers from P. Hermes in its less oblique I'orm, shorter liiniie- 

 line, less ample umbo, and in having no regular alternation in the ra^s, which 

 are closer and more rounded. It is associated with, and closely allied to, P. dig- 

 natus, but dillers by its more obtuse beak, longer outline, and comparatively 

 more frequent and smaller rays, witiiout tlie regular concentric striag. 



Formation and locality. In the Marcellus shale at Bloomlidd, Ontario 

 county. N. Y. 



Pterinopecten Hermes. 



IT.ATE XVII, FUJS. l:t-15. 



Ptfrinnptiltn Htniie.i. Ham,. Pal. N. V.. vol. v, pt. 1. Plates and Explanations: PI. 17. liys. 13-15. 



.Ian., 1883. 



SiiKLi. less than medium size, sub-rhomboidal, obliquely sub-ovate; length and 

 height about as three to four ; pallial margins regularly rounded, becoming 

 straight on the post-cardinal slope at the junction with the ear. 



Left valve moderately convex. Right valve not determined. 



Beak acute, prominent, iintcrior to the middle ol' tlir slidl (liiectcd tin ward. 

 Umbonal region ninplf, subtending an angle of al)Out 80°. 



Ears very uueijual, triangular. Posterior ear much the larger, scarcely 

 defined ; margin concave ; extremity acute. Anterior ear small, slightly 

 C(mvex, defined by a distinct sulcus ; margin convex ; extremity rounded. 

 Byssal sinus deep. 



Test marked by regular, rounded stria\ with wider interspaces which, on 

 the posterior part of the valve, show finer intermediate rays. The ears 

 have essentially the same surface characters as the body of the valve. The 

 entire surface is marked b\ fine ccmcentric stria*. Umbo with concentric 

 wrinkles. Partial casts of the interior sliow the same characters as the 

 exterior, liut show no iiuisculiir or pallinl iiiaikings. 



