NOTICE OF PALiEONTOLOGY OF NEW -YORK, VOLUME IV. 167 



Fig. 2.^ 

 Longitudinal section of the dorsal valve. 



j. Cardinal process. 



b. Tooth-socket. 



c. Crural processes. 

 I. Loop. 



s. Septum. 



In the punctate texture of this shell, it differs from either of the Genera 

 Lept^na, Strophomena or Strophodonta; but this might not be an 

 objection to admitting Tropidoleptus into the family, were the other 

 characters coincident. The area is longitudinally striated, and presents a 

 different aspect from any of the Strophomenid^, but has analogy with 

 some of the Orthides. The teeth are not extensions of the lamellae bounding 

 the foramen, but distinct from it and deeply crenulate or lobed, and inserted 

 into corresponding crenulate sockets in the dorsal valve. The form of mus- 

 cular impressions, so far as known, is not very dissimilar to those of Stro- 

 phomena or Orthis. 



In comparing the form of the cardinal process and its appendages, we 

 shall find it almost entirely similar to that of Leptoccelia, as shown in 

 two authentic species [L. Jiahellites and L. Jimbriata), and the muscular 

 impression of the ventral valve is quite like that of the same species. 



The exterior extremity of the cardinal process presents considerable 

 variety of aspect, when a large number of individuals are examined. In 

 some of them this part, if stripped of the external callosity of pseudo- 

 deltidium, would have the main process bilobed, with a sinus a little below 

 the apex, and an accessory lobe on each side similar to some of the species 

 of Productus. 



The T. carinatus is the typical species ofi the genus. A western form has 

 been described under the name T. occidens. 



The relations of the Genus Vitulina are not fully established. The 

 shell-structure is punctate, with a papillose surface, a high area on the ven- 

 tral valve, with a large triangular fissure. The genus embraces a single 

 species, the VitvZina pustulosa. 



Note. — At the time of writing this notice, it was intended to be published with the 

 date of its writing, and the first sixteen pages were then put in type ; but other duties 

 intervening, it was not again taken up until February, and now bears the imprint of 

 March. In the meantime the letter press of Vol. IV has been published. 



