488 PALEONTOLOGY OF NEW YORK. 



PALiEANATINA, Hall. 1870. 

 Pal^anatina typa, Hall. 1870. 



I'LATE I.XXIX, FIGS. 2t^-28, 85-S7. 



PalaatuUitM typ<i, Sai,l. Pi-elim.Notice Lamellibi-anchiata, 2, p. 85. 1870. 



In part " " " Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 79, fiffs. 20-39. 1883. 



Shell short-soleniibrni, elongate, sub-elliptical; length twice the height; basal 

 margin slightly sinuate in the middle, often nearly straight and sometimes 

 gently curving. Posterior extremity abruptly rounded, often sub-truncate. 

 Cardinal line straight, or slightly arcuate. Anterior end short, regularly 

 rounded. 



Valves unequally convex, and apparently slightly gaping at both extrem- 

 ities. Left valve somewhat gibbous in the umbonal region. Right valve 

 depressed-convex. 



Beaks in advance of the anterior third, appressed, rising but little above 

 the hinge. Cincture very broad, undefined, affecting the lower half of the 

 valve, producing a broad sinuosity in the margin. Umbonal slope obtusely 

 sub-angular, extending to the post-inferior extremity. Cardinal slope nearly 

 Hat or slightly concave, with a narrow fold developed near the cardinal line. 



Surface marked by fine concentric striae, which are frequently irregularly 

 fasciculate on the basal portion of the shell. 



Four specimens measure respectively 16, 20, 28 and 31 mm. in length, 

 and 7.25, 10, 14 and 15 mm. in height. 



The shells of this species vary considerably in form and expression. The 

 umbonal ridge and the post-cardinal fold are variously developed, the umbonal 

 slope being often scarcely angular, and the fold on the cardinal slope some- 

 times obsolete. The cincture is also sometimes excessively developed, produc- 

 ing a deep and broad sinuosity in the margin. But few specimens of the right 

 valve have been observed ; these are depressed, the umbonal slope subdued, the 

 l)eaks inconspicuous and without any evidence of a fold on the cardinal slope. 



Formation and locality. In the conglomerate of the Chemung group, at Port- 

 ville, Cattaraugus county, N. Y. 



