LAMELLIBRANCHIATA. 303 



distinctly angular, descending in nearly a direct line to the post-basal 

 extremity. 



Test of moderate thickness ; the cast is marked by fine concentric strife, 

 which are strongly fasciculate on the anterior portion of the shell, and regu- 

 lar and uniform in strength on the post-cardinal slope. Interior unknown. 



The specimen described has a length of 72 mm. and a height of 35 mm. 



This species, compared with any other, has a much greater elevation of the 

 umbo above the base of the shell, a larger anterior end and a more rapid 

 declension to the post-basal extremity. The figure of this species given on 

 plate xliv does not correctly represent the specimen. 



Formation and locality. In the Chemung group, near Franklin, Delaware 

 county, N. Y. 



GONIOPHORA ChEMUNGENSIS. 



I'LATK XLIV, FIGS. 18, 20, 22. 



Cffpricarditen Chemungensin, Vaxixkm. Geol. Surv. N. Y., Reji. Thii-il Dist., p. 181, tig. 2; p. 170. 1842. 



Saiiffuiiwlitet Chemii.ii(jfmis, " S. A. Miller. Cat. Amer. Pal. Foss., p. 202. 1877. 



Chmkrphora Chemungetisis (Vani-xkm), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 44, 



figs. 18-22. 1883. 

 Cypricarditeg carinifera, Conrad. Jour. Acail. Nat. Sci., Phila., vol. viii, p. 245, pi. 13, fig. 14. 1842. 



Shell large, trapezoidal ; length two and one-half times the height ; basal 

 margin very gently curving, nearly straight, or slightly sinuate anterior to 

 the middle ; posterior extremity obliquely truncated. Cardinal line straight, 

 parallel to the base, extending for nearly two-thirds the length of the shell. 

 Anterior end sloping rapidly from the beak and abruptly rounded below, 

 limited by a very oblique, narrow, undefined sinus, which reaches the base 

 more than one-third of the length from the anterior end. 



Valves moderately convex on the lower side, becoming gibbous in the 

 umbonal region. Post-cardinal slope fiat or slightly concave. 



Beaks sub-anterior, small and closely incurved, situated less than one- 

 fourth the length of the shell from the anterior extremity. Umbo prom- 

 inent. Umbonal ridge distinctly angular, extending in a direct line or with 

 a gentle curvature to the post-basal extremity. 



