LAMELLIBRANCHIATA. 413 



angle to the anterior end are very strong and elevated, obscuring the radii. 

 Interior unknown. 



All the specimens known are much distorted by pressure, and the entire 

 characters cannot be determined. 



One specimen has a length of 19 mm. and a height of 9 mm. A large 

 specimen measures 25 mm. in length. 



Formation and locality. In the shales of the Hamilton group, at York, Living- 

 ston county, N. Y. 



CONOCARDIOM DENTICULATUM. 



PLATE I.XVni, FIGS. 24, 35. 



Cortocardium denticulatuin. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 68, figs. 24, 25. 



1883. 



Shell small, ovate-cuneate ; basal margin straight. Body gibbous, truncate 

 behind, abruptly contracted and attenuate in front. 



Body of the shell marked by five or six strong angular radii ; those of the 

 post-cardinal slope unknown. The anterior end is cancellated by fine radii 

 and lamellose concentric striae. The interspaces between the strong radii 

 are marked by fine concentric striae. Anterior portion of the shell gaping, 

 the margins of the valves furnished with distant lamelliform denticulations. 

 Interior unknown. 



The fragment described has a length of 10 ram. and a height of about 5 mm. 



This form differs from C. Eboraceum in the strong angular radii upon the 

 body of the shell ; the post-cardinal area is smaller and the anterior portion 

 more contracted and attenuate, with much finer radiating and concentric strise. 



Formation and locality. In the shales of the Hamilton group, at York, Liv- 

 ingston county, N. Y. 

 53 



