106 
PALAEONTOLOGY OF NEW-YORK. 
142. 5. LEPTaENA CAMERATA. 
Pl, XXXI. A. Figs. 2 a, b. 
Strophomena camerata. Conrad, Jour. Acad. Nat. Sciences, pag. 254, pl. 14, fig, 5. 
Compare Leptcena ddtoidca, Conrad, and the figures of that species in this work. 
Suborbicular; dorsal valve very ventricose in the middle, abruptly elevated in front; 
disk and umbo nearly flat, or depressed convex ; surface marked by numerous crowded 
unequal radiating striae ; extremities of the hinge line slightly salient, and constricted 
below ; apex scarcely projecting beyond the hinge margin. 
The shell is removed from this specimen, except on the disk of the dorsal valve. Near 
the extremity of the hinge line, and on the disk, there are some obscure wrinkles, which 
induce me to believe that this shell is only a variety of L. deltoidea of Conrad. The 
specimen figured, however, I believe to be the original one from which Mr. Conrad has 
drawn his description, otherwise I should not have ventured a separation from L. deltoidea. 
Fig. 2 a. Lateral view of the specimen, showing the extreme convexity of the shell in the centre, and 
the nearly flat disc. 
Fig. 2 b. Front view, showing the great deflection; the surface is puncto-striate, from being denuded of 
the shell. 
Position and locality. In the Trenton limestone at Trenton Falls. {State Collection.) 
143. 6. LEPTiENA DELTOIDEA. 
Pl. XXXI. A. Figs. 3 a, b, c, d, e. 
Leptcena deltoidea. Conrad, Ann. Geol. Report, 1838, p. 115; 
Strophomena deltoidea. Id. Ib. 1839, p. 64; 1841, p. 37. 
— — Vanuxem, Geol. Report, 1842, pag. 46, fig. 2. 
— — Emmons, Geol. Report, pag. 389, fig. 2. 
Shell semioval or deltoid ; hinge line extending beyond the width of the shell; dorsal 
valve convex, abruptly deflected at the margin, except a small portion in the centre, which 
is often produced in front; surface of the disc marked by numerous irregularly concentric 
undulations or wrinkles, which are crossed by fine equal radiating striae ( one or tw T o of 
these striae, in the middle of the shell, more prominent than the others); sides of the shell 
marked only by the finer striae ; sometimes, in well marked specimens, the striae are 
distinctly alternating ; disc elevated in the middle; beak scarcely projecting beyond the 
cardinal line. 
This shell differs from the preceding species, in the usually more convex area or disc of 
the dorsal valve, and the linguiform extension in front, which, though existing in the 
nasute forms of the L. alternata , is not accompanied by the concentric wrinkles. This 
feature characterizes nearly all the specimens I have seen from Trenton Falls. 
