284 Thirty-fifth Keport on the State Museum. 



PTERINEA, Goldfuss. 



Pterinea grandis. 



Pterinea grandis, Hall. Pal. N. Y., vol. v, pt. 1. Unpublished. 



Shell very large, capacious, oblique, sub-rkomboidal, body broadly 

 ovate ; length about one-fifth greater than the height ; margins 

 regularly rounded, broad along the base, and a little produced on 

 the posterior side. Left valve convex. Right valve unknown. 

 Hinge-line straight, apparently somewhat less than the length of 

 the valve (imperfect in the specimen). Beak obtuse, prominent, 

 directed forward. Umbonal region gibbous, subtending an angle 

 of about 90°. Wing large, triangular, not distinctly defined, mar- 

 gin rounded, with a gentle concavity near the junction of the valve. 

 Ear not observed. 



Test thick, marked by distant, strong radii from the umbo to the 

 base; the interspaces having alternating larger and smaller rays ; 

 crossed by concentric, undulating lamellose striae of growth. 



The specimen has a length of 120 mm., height 100 mm., and the 

 hinge-line, from the beak to the extremity of the wing, 95 mm. 



This species is distinguished by its large size, very distant strong 

 radii, and convexity. Compared with P.flabella, it is proportionally 

 longer, and the wing less defined. Compared with P. pinguis, it dif- 

 fers in greater length and somewhat less gibbosity. 



Formation and locality. In the upper Helderberg limestone in 

 Scott county, Indiana. 



Pterinea pinguis. 



Pterinea pinguis, Hall. Pal. N.Y., vol. v, pt. 1. Plates and Explanations: PI. 

 15, figs. 2, 3. Jan., 1883. 



Shell large, gibbous, obliquely ovate, length and height nearly equal; 

 pallial margins rounded, produced on the posterior basal side, and 

 concave at the junction of the wings. Left valve ventricose, sub- 

 angular along the anterior side. Right valve unknown. Hinge- 

 line straight, nearly central ; length somewhat greater than the 

 length of the shell. Beak acute, angular, arching over the hinge, 

 situated near the anterior extremity of the hinge-line, directed 

 forward. Umbonal region prominent, ventricose, defined, subtend- 

 ing an acute angle. Wing large, triangular, limited by the rapid 

 post-cardinal slope of the valve ; margin slightly concave, rounding 



