104 
PALAEONTOLOGY OF NEW YORK. 
VERTUMNIA, n. s. g. 
Pterinea (Vertumnia) reversa. 
PLATE XXIV, FIGS. 6, 12; and PLATE LXXXIV, FIG. 2L 
Pterinea reversa, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 24, figs. 6, 12. 
Jan., lSSiL 
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 fiat, 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 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 indefiniteness of 
the cardinal expansions, the convexity of the right valve, and the flat or con¬ 
cave character of the left valve. 
Formation and locality. In the Chemung group near Elmira, at the Upper 
Narrows of Chemung river, N. Y., and in Tioga county, Pa. 
