LAMELLIBRANCHIATA. 411 



. CONOCARDIUM OhIOENSE. 



PLATE LXVIII, FIGS. 2, 3. 



Conocardium Ohioenxe, Meek. Proc. Acad. Nat. Sci., Phila., p. 9. 1871. 



" " Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 68, tigs. 2, 3. 



1883. 



Shell small, ovate, sub-trigonal, ventricose behind the middle of its length ; 

 length one-third greater than the height. Posterior end prominent, pro- 

 duced in the middle and sloping abruptly to the post-cardinal angle. Ante- 

 rior end abruptly contracted in front of the middle and prolonged, nasute, 

 with the extremity narrowly rounded. 



The body of the shell is marked by about six strong radiating plications 

 on the ventricose portion of the valve, and on each side by more numerous 

 and smaller plications. The interspaces between the ribs are marked by 

 lamellose concentric striae. 



A specimen of this species has a length of 15 mm. and a height of 10 mm. 



This species differs from C. cuneus in being more narrowly ventricose, and 

 the body of the shell marked by fewer plications, with a distinct constriction 

 in front ; the umbonal slope is more rounded and less oblique, while the poste- 

 rior extremity is more produced than in the usual forms of C. cuneus and C. 

 trigonale. 



Formation and localities. In the Corniferous limestone, near Columbus, Ohio, 

 and at the falls of the Ohio river. 



CONOCABDIUM NORMALE. 



PLATE LXVIII, FIGS. 17-19. 



Conocardium nonnale. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 68, tigs. 17-19. 1883. 



Shell large, sub-ovate, trigonal ; length about twice the height ; basal margin 

 regularly curving. Posterior extremity obliquely truncate. Cardinal line 

 straight. Anterior end narrow, nasute. 



Valves ventricose, abruptly contracted anteriorly and truncate behind. 



Beaks posterior to the center, prominent, strongly incurved. Umbonal 



