﻿280 CONRAD'S DESCRIPTIONS OF 



centrica, Rauliniana, radiata, gibbosa and circinalis of D'Orbigny have all an external 

 resemblance to the genus Linearia. I have not seen a species from any American 

 Tertiary formation. 



KELLIA, Turtm. 



Kellia cretacea. PI. 46, fig. 19. Oval, compressed, subequilateral, the anterior 

 side rather longest ; surface entire ; posterior end obtusely rounded ; posterior dorsal 

 and basal margins moderately arcuated. 



Locality. — Eufaula, Alabama. Tuomey's collection. 



SPH^RELLA, Conrad. 



Globose, thin, cardinal plate narrow ; posterior cardinal tooth of right valve broad, 

 erect, bifid, parallel with the hinge margin ; anterior tooth very small, pyramidal, 

 not oblique ; anterior tooth in the left valve triangular, small, pyramidal, entire ; 

 posterior tooth elongated, much compressed, very oblique ; muscular impressions very 

 large. 



This genus having generally been undistinguished from Diplodonta, I have given 

 a full generic character, and in addition I may remark that the anterior cardinal 

 margin is extended as a carina, considerably beyond the apex, which is not the 

 case in Diplodonta : the muscular scars are much larger and longer than in that 

 genus and extend nearer to the ventral submargin. The prominent summit and 

 great capacity of the umbo will alone distinguish this genus at a glance from Diplo- 

 donta. 



The recent species are D. orbella, Gould, a Californian shell ; Lucina costata from 

 Guayquil, and L. Novo-Zelandia, from New Zealand. Thus the genus in the 

 recent state belongs to the Pacific fauna, and in a fossil state is peculiarly 

 American. All the species of Diplodonta in Bronn's Lethea have the characters of 

 the typical species so well defined that no one of them can be referred to Sph&rella. 



The first appearance of this genus is in the Cretaceous formation, as indicated by 

 the species herein described. In the Eocene of Alabama, or of the other Southern 

 States, I have never found a species, but I obtained four species of Diplodonta. In 

 the Miocene there are two species of Diplodonta and only one of Sph^erella. 



Sph^erella concentrica. PI. 46, fig. 4. Subglobose, thin and fragile, equilateral, 

 concentrically striated, strise prominent and acute except on the umbo, where they 

 are rugose and minute ; summit prominent, smooth ; umbo inflated and very 

 ventricose. 



Locality. — Eufaula. Tuomey's collection. 



