LAMELLIBRANCHIATA. 485 



Cypricardinia indenta. 



PLATE LXXIX, FIGS. 6-16, 23 ; AND PLATE XCVI, FIG. 2. 



Cypricardites indenta, Conrad. Jour. Acad. Nat. Sci., Phila., vol. viii, p. 244, pi. 12, fig. 12. 1842. 

 In part Cypricardinia indenta (Conrad), Hall. Prelim. Notice Lamellibranchiata, 2, p. 83. 1870. 



Pal. N. Y., vol. V, pt. 1. Plates and Explanations : 

 PI. 79, figs. 6-23. 1883. 

 Cypricardites inflata, Conrad. Jour. Acad. Nat. Sci., Phila., vol. viii, p. 246, jil. 15, fig. 2. 1842. 



Shell of medium size, sub-rhomboid-ovate ; length more than one-third greater 

 than the height; basal margin nearly straight, slightly sinuate anterior to 

 the middle. Posterior extremity abruptly rounded below and obliquely 

 truncate above. Cardinal line straight, oblique. Anterior end very short, 

 rounded below. 



Right valve very convex, often extremely gibbous. Left valve usually 

 depressed-convex below and posteriorly, becoming moderately gibbous in the 

 umbonal region. 



Beaks nearly anterior, small and appressed, rising but little above the 

 hinge-line. Cincture distinct on the right valve, less marked upon the left 

 valve. Umbonal slope rounded and prominent on the right valve, sub- 

 angular on the left valve. 



Surface marked by extremely fine concentric striae and by unequally distant 

 but somewhat regular, lamellose, imbricating, concentric undulations ; and in 

 well-preserved specimens the entire surface is marked by fine striae, which radi- 

 ate from the apex of the shell, and in some conditions of preservation the sur- 

 face shows a second set of striae vertical to the direction of the lamellae. 



Four specimens measure respectively 11, 14, 18 and 20 mm. in length, 

 and 7, 8, 11 and 11 mm. in height. 



This species is smaller than the preceding, the right valve, when well- 

 preserved, is more gibbous, the depression or sinus above the umbonal slope is 

 not so distinctly defined, and the posterior margin is not sinuate. This spe- 

 cies probably includes the form described as Cypricardites inflata by Mr. Conrad, 

 which represents a gibbous specimen as preserved in the limestone. The speci- 

 mens, figs. 6, 7, 8, are from near the original locality of that species. 



Formations and localities. In the Corniferous limestone, at Babcock's hill, 

 62 



