294 Thirty -fifth Report on the State Museum. 



VERTUMNIA (subgenus). 



Pterinea (Vertumnta) reyersa. 



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

 24, figs. 6, 12. Jan., 1883. 



Shell large, rhomboid-orbicular ; body somewhat oblique ; length 

 and height nearly equal ; margins regularly rounded, a little more 

 extended on the posterior side. Left valve flat, or slightly concave, 

 except near the umbo. Right valve moderately convex, the greatest 

 convexity about the middle of the height. Hinge-line straight, 

 length equal to the length of the valve, extending anteriorly 

 beyond the margin. Beak of left valve depressed, obtuse, unde- 

 fined, erect. Beak of right valve low, obtuse, inclined forward. 

 Umbo not distinct in either valve. Ear of the right valve limited 

 by a distinct broad byssal smus. Wing triangular, undefined. 



Surface marked by strong, rounded, simple, continuous radii 

 originating upon the umbo; with wide, flat interspaces, which, 

 in the right valve, show occasionally a finer ray; crossed by regu- 

 larly arranged, sharp, concentric striae, which are conspicuous both 

 on the rays and interspaces. The rays are obscure and distant on 

 the upper part of the cardinal expansions. 



A large right valve has a length of 50 mm., height 47 mm., 

 hinge-line 55 mm. 



This species differs from P. prora by its lesser obliquity, the in- 

 defmiteness of the cardinal expansions, the convexity of the right 

 valve, and the flat or concave character of the left valve. 



Formation and localities. In the Chemung group near Elmira, at 

 the Upper Narrows of Chemung river, N". Y., and in Tioga county, 

 Pa. 



Pterinea (Vertumnia) avis. 



Pterinea reversa var. avis, Hall. Pal. N.Y., vol. v, pt. 1. Plates and Explana- 

 tions ; PI. 24, figs. 9, 11, 13. Jan., 1883. 



Shell of medium to large size, rhomboidal, oblique ; Jbody ovate ; 

 length greater than the height ; margin moderately rounded in front, 

 becoming full on the posterior side. Left valve depressed-convex 

 above, flat or concave below. Right valve convex; the greatest 

 convexity about the middle of the valve. Hinge-line straight, 

 length greater than the length of the shell, extended anteriorly be- 



