OMSK ANY SANDSTONE. 
Eatonia pnmila ( n. s.). 
Plate Cl. Fig. 1. 
Shell small; length and breadth nearly equal. Cast of the ventral valve 
flat in the middle and deeply sinuate in front; margins crenulate 
below the middle of the shell; beak acute ; cavities of the teeth deep 
and strong : muscular area narrow, the points of the adductor muscle 
being visible only under a lens. The medio-longitudinal ridge is con¬ 
tinued below the middle of the valve. 
This small species has been recognized only in the cast of a ventral valve, which 
is very distinct from any of the others in its narrow elongate muscular impression 
and pointed beak. The surface has probably been finely striated, like the E. pe¬ 
culiars and E. singularis. 
Fig. 1. The cast of the ventral valve, natural size. 
Geological position and locality. In the Oriskany sandstone : Albany county. 
Eatonia wliitfieldi (n. s.). 
Plate Cl A. Fig. 2 a, b. 
Shell longitudinally suboval, wider below than above. Ventral valve de¬ 
pressed convex near the beak, flat in the middle, and broadly depressed 
towards the front. 
Surface radiatingly plicated : plications rounded, about eight or nine on 
each side of the mesial one, which is a little stronger than the others. 
Muscular impression of the ventral valve broad, and not strongly defined : 
crural processes short. 
The specimens examined are an imperfect ventral valve, and another ventral 
valve preserving the beak of the dorsal valve and the crural processes in part. 
Fig. 2 a. The exterior of the ventral valve. 
Fig. 2 b. The interior of the ventral valve, with the apex of the dorsal valve attached. 
The specimens yet obtained are too imperfect to give more complete illustrations. 
Geological position and locality. In the Oriskany sandstone : Cumberland, Md. 
