LAMELLIBRANCHIATA. 295 



Test marked by strong concentric striae, which are acutely recurved upon 

 the umbonal angle. 



In the specimen figured on plate xxxv the umbonal ridge, in the middle of 

 its length, has been accidentally flattened and the stronger stria? crossing 

 this flattened area are preserved, showing only a gentle curve in their 

 direction instead of sharply recurving over the angular portion of the ridge. 



Interior essentially unknown. 



A specimen of medium size has a length of 75 mm., and a height of 45 

 mm. A smaller individual has a length of 60 mm., and a height of 35 mm. 

 One large specimen has a length of 90 mm. 



This species differs from all others here described in the extremely expanded 

 and alate cardinal slope. 



Formation and locality. In the Schoharie grit, Schoharie, N. Y. 



GONIOPHORA ACUTA. 



PLATE XLIII, FIGS. 1-3. 



Sanguinolitai acutuJt, Hall. Pi-elim. Notice Lamellibranchiata, 2, p. 37. 1870. 



" " S. A. MiLi-KB. Cat. Amer. Pal. Foss., p. 202. 1877. 



Ocnilophora acuta. Hall. S. A. Millbr. Cat. Amer. Pal. Foss., p. 192. 1877. 



" " " Pal. N. Y., vol. V, pt. 1. Plates and Explanations: PI. 43, figs. 1-3. 1883. 



Shell large, trapezoidal, very much elongated posteriorly; length more than 

 twice the height; basal margin straight on the posterior part with a sinus 

 anterior to the middle, beyond which it curves into the anterior margin; 

 posterior margin obliquely truncate ; cardinal margin nearly straight, or 

 slightly arcuate, extending nearly two-thirds the length of the shell. 

 Anterior end short, rounded below, limited by an oblique sinus extending 

 from the beak to the base, just anterior to the middle. 



Valves convex below the umbonal ridge, depressed at the sinus, slightly 

 concave between the umbonal ridge and the cardinal line. 



Beaks anterior, small, closely incurved. Umbonal ridge angular, prominent, 

 extending to the post-basal extremity. 



Test moderately thick, marked by closely arranged sub-lamellose striae. 



