122 TRANS. OF THE ACAD. OF SCIENCE. 
hime: with a line of closely-set oblique teeth on each side & 
the be 
Length, 20 lines; height, 10 lines. 
The specimens in the collection were obinioed by D Dr. Er 
ans mg the writer, in the autumn of 1851, from the 
surfaces drate 
of iron. ‘Dab of the specimens, a savelah of the exterior shows 
the surface markings very plainly. 
Prctrn Coosensis, Shumard. 
Shell large, suborbicular, much maemnieannd valyes flatten 
ed « convex, the superior one more depressed ‘than the 0 5 
surface ornamented with focus twenty-seven to “one 
thirty. 
