CHONETES OP THE CORNIFEROUS LIMESTONE. 133 



than in C. lineata. In the dorsal valve of the former, the muscular impression, 

 base of cardinal process, etc. are strongly defined, while they are not so in C. 

 lineata. 



This species diflfers from C. pusilla in its much finer and more numerous striae ; 

 while it is smaller and more rotund than C. scitula of the Hamilton group. 



The characters of the species are illustrated in figures 3 a-f, on Plate xx. 



Geological formation and localities. In the Corniferous limestone at Oneida 

 falls, and abundant between Jamesville and Manlius in Onondaga county, and in 

 the north part of Seneca county. It is less abundant in the eastern localities of 

 the Corniferous limestone, and also- in the extreme western localities ; but it has 

 been found on the Indian Reservation near Bufi"alo. 



Clionetes yandellana. 



PLATE XX. 



Chonetet yandellana : Hall in Tenth Report on the State Cabinet, p. 118. 1857. 

 Compare C. lineata, ut sup. page 121. 



Shell semioval, more or less gibbous : hinge-line equalling the greatest 

 width of the shell. 



Ventral valve regularly convex, abruptly depressed towards the cardinal 

 angles, which are nearly flat and very slightly deflected to the ventral 

 side. 



Dorsal valve with the concavity a little less than the convexity of the 

 opposite valve. 



Area of the ventral valve parallel with the longitudinal axis of the shell, 

 nearly twice as wide in the middle as near the extremities : foramen 

 comparatively large, with margins projecting, and the opening filled 

 by the cardinal process of the opposite valve. Dorsal area extremely 

 narrow, being barely a defined line. 



Surface, marked by fine somewhat equal strioB, which increase by 

 bifurcation and intercalation till there are from sixty to seventy on 

 the margin of the shell. The cardinal margin of the ventral valve 

 bears three or four short oblique spines on each side of the centre. 

 The interior of the ventral valve shows strong dental lamellae, and the 



muscular impressions are pretty well defined. The dorsal muscular 



