CHONETES OF THE CORNIFEROUS LIMESTONE. 
123 
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 differs from C. pusilla in its much finer and more numerous strise ; 
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 Buffalo. 
Chonetes yandellana. 
PLATE XX. 
Chonetes 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 : binge-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 striae, 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 
