ini PALAEONTOLOGY OF NEW YORK. 



VERTUMNIA, n. s. g. 

 Pterinea (Vertumnia) keversa. 



PLATE \\1\, FIGS. 6, 18; am. PLATE I.XXX1V, FIG. -I 



J>| riltea IYWM, Ham.. Pal. N. V., vol. v. pt. 1. Plates anil Explanations: PI. 24, tiurs. B, 12. 



Jan., 1S83. 



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

 nearly equal; margins regularly rounded, a little more extended on the pos- 

 terior 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, undefined, 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 sinus. Wing 

 triangular, undefined. 



Surface marked by strong, rounded, simple, continuous radii which 

 originate upon the umbo; with wide, flat interspaces, which, in the right 

 valve, show occasionally a finer ray; crossed by regularly arranged, sharp, 

 concentric striae, which are conspicuous both on the rays and interspaces. 

 The ra\ s are obscure and distant on the upper part of the cardinal expansions. 



A large right valve has a length of 50 mm., height -17 mm., hinge-line 

 ■V> nun. 



This species differs from P. prora by its lesser obliquity, the indefiniteness of 

 the cardinal expansions, the convexity of the right valve, and the Hat or con- 

 cave character of the left valve. 



Formation and locality. In the Chemung group near Ehnira, at the Upper 

 Narrows of Chemung river, X. V.. and in Tioga county. Pa. 



