CONTRIBUTIONS TO PALEONTOLOGY. 



121 



XL ON THE GENUS TROPIDOLEPTUS.* 



The Genus Tropidoleptus was proposed by me in the Tenth Report on 

 the State Cabinet, published in 1857. The shell made the type of the 



Fig. 1. 



Fig. 2. 



genus was the Strophomena cari- 

 nata, Conrad, published in the 

 Annual Report on the Palaeontology 

 of the State for 1859. At the 

 time of proposing this generic 

 name, very little was known of 

 the interior structure of the shell, and it was separated on account of 

 hinge structure and the punctate texture of the shell. 



The accompanying figures will give a general idea of the form and 

 exterior character of the Tropidoleptus carinatus. Fig. 1 is a dorsal view, 

 with the surface partially covered by a delicate bryozoan ; fig. 2 is a 

 ventral view. 



In 1850, I had obtained some further knowledge of the interior, as 

 represented in fig. 3 of the interior of the ventral valve, showing the area, 

 foramen, teeth, etc., enlarged; 

 and fig. 4 of the interior of 

 the dorsal valve, showing 

 the cardinal process, the den- 

 tal fossets, the bases of the 

 crura, and the septum. 

 There seemed still some- 

 thing not quite understood in regard to its interior 

 structure ; and it was only as the description was going to press in Vol. 

 iv, following the Strophomenidas, that I resolved to make some further 

 eflbrts to discover its entire structure ; which resulted in determining 

 the characters of the loop illustrated in figs. 5 and 6, page 323. In 

 placing the genus at the end of the volume, and following Terebratula 



* This paper was communicated to the Nineteenth Report on the State Cabinet, but not printed. 

 The Notice of Vol. iv, Palanntology of New Yorlc, published in the present Report, in which the 

 observations on this genus are cited, causes some unavoidable repetition. 

 Cab. Nat. 41 



