370 
PALEONTOLOGY OF NEW YORK. 
Selenella gracilis, sp. nov. 
(See page 270, figs. 184-186.) 
Oriskania navicella, sp. nov. 
PLATE LXXLX, FIGS. 25-27. 
(See pages 269, 270, figs. 181-183.) 
RENSSEL./ERIA CaYUGA, Sp. nOV. 
PLATE LXXV, FIGS. 1, 2. 
Shell lenticular, often of large size ; suboval in marginal outline. Valves 
subequally biconvex, sloping regularly in all directions. Apex of the pedicle- 
valve scarcely prominent; umbo not conspicuous, sometwhat elevated medially. 
Divergent cardinal ridges and cardinal slopes well defined. Brachial valve 
with apex depressed and concealed; somewhat less convex in the umbonal 
region than the opposite valve. Surface of both valves covered with a great 
number of fine, simple, thread-like, rarely duplicating plications, of which 
from seventy to one hundred may be counted on each valve near the anterior 
margin. 
Oriskany sandstone. Cayuga, Ontario. 
Beecheria Davidsoni, nom. nov. 
PLATE LXXIX, FIGS. 33-36. 
(See page 300, fig. 224.) 
