1U4 PALEONTOLOGY OF NEW YORK. 



VERTUMNIA, n. s. g. 

 Pterinea (Vertumnia) keversa. 



I'l.ATK XXIV, FIGS. G, li ; AND I'l.ATK I.XXXIV, KIU. U. 



PUriiiea rrirrxa, Hai.i.. Pal. N. Y., vol. v. jit. 1. Plates and Kxplanatioiis : PI. 24. Hi.'-.-;. H, 12. 



Jan., 1883. 



SiiKi.L large, rhomboid-orlncular ; l)0(l_v soiiicw liat oMique; Iciigtli ami licight 

 nearly equal; margins regularly rouiidiMl, a little more extemlcil on the pos- 

 terior side. 



Left valve flat, or .slightly concave, except near the iiniho. Right \al\e 

 moderately convex, the greatest convexity ahoiit the inidillc of the lici-iit. 



Hinge-line .straight, length ('(inal to the length ol' the valve, e.xteiiding 

 anteriorly beyond the margin. 



Beak of left valve depressed, obtuse, undelineil, erect. Beak of right valve 

 low, obtuse, iiH lined 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, sinij)le, continuous radii which 

 originate upon the umbo; with wide. Hat interspaces, which, in tiie 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 5() mm., height 47 mm., hinge-line 

 0-5 mm. 



This species differs IVnni /'. prora by its lesser obliquity, the indefiniteness of 

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

 cave character of the left valve. 



Formation and locality. In the Chemung group near Elmira, at the L'j)2Jer 

 Narrows of Chemung river, N. Y., and in Tioga count}^ Pa. 



