106 PAUBONTOLOGY OF NEW-TOKK. 



142. 5. LEPTiENA CAMERATA. 



Pl, XXXI. A. Figs. 2 a, b. 



Strophontena eameraia. Conbac, Jour. Acad. Nat. Sciences, pag. 254, pi. 14, fig. S. 

 Compare LepUena delloidta, Conkax), and the figures of that species in tliis 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 tliis 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. LEPT^NA DELTOIDEA. 



Pi.. XXXI. A. Figs. 3 a, b, c, d, e. 



Leptana deltoidea. Conkad, Ann. Geol. Report, 1838, p. 115; 

 StTophomena deltoidea. Id. lb. 1839, p. 64; 1841, p. 37. 



— — Vanuxem, Geol. Report, 1842, pag. 46, fig. 2. 



— — Emmohs, 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 two 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 strias are 

 distinctly alternating ; disc elevated in the middle ; beak scarcely projecting beyond the 

 cardinal line. 



This shell diflfers 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. altemata, is not accompanied by the concentric wrinkles. This 

 feature characterizes nearly all the specimens I have seen from Trenton Falls. 



