S. W. Ford— Primordial fossils of Rensselaer Co.. N. ¥Y. 218 
Troy ; and also, doubtfully, in the condition of casts, in even- 
bedded limestone of the same locality. Collected by the writer. 
Obolella nitida, sp. nov. 
becoming more shallow till it disappears. portion of the 
dorsal valve close to the margin is sometimes nearly flat all 
around. The internal markings are not well enough shown in 
any of the specimens that I have seen to admit of description. 
The surface is ornamented with very fine concentric striz and 
numerous close-set radiating strise, the whole just visible to the 
unassisted eye. : 
The ventral valve is not certainly known. The width of the 
largest dorsal valve that I have seen is 0°14 of an inch and the 
length 0-10 of an inch. : 
Occurs in both even-bedded and conglomerate limestone of 
the Potsdam group at Troy. Collected by the writer. 
Scenella retusa, sp. nov. 
