88 



The under side of this fossil, showing the mouth and dentated lip of 

 N. conoidea, is represented Plate VI. Fig. 6. 



This, with another specimen, in which the cast is entirely detached 

 from the shell, was purchased from the Callonnean collection, and is from 

 Courtagnon. 



I have the N. conoidea, in very good preservation, from the Valley 

 of Ronca. 



Lamarck particularizes three species of this genus as being found 

 among the French fossils : N. conoidea, N. tricarinata, N. mammaria. 



LX. Natka. A nearly globose umbilicated univalve : the opening 

 entire and semicircular ; the columella transverse, without teeth, and 

 callous externally ; the callosity narrowing, or even covering, the um- 

 bilicus. 



These shells bear considerable resemblance to Nerita, in the form of 

 their opening ; but they obviously differ from the shells of that genus, 

 in always being umbilicated, and never having their columella dentated. 



Natica cepacea, Lam. is a species remarkable for its flattened roundish 

 form, and still more for the large thick callous mass, w r ith which the 

 umbilicus is covered, in the adult specimens. N. canrena is a frequent 

 fossil in the Essex bank of fossil shells. Another species of this genus is 

 also frequently found in this bank, which is figured by Dale, History 

 and Antiquities of Harwich, Sfc. PL x. Fig. 16, and by him referred to 

 Cochlea sublivida orefusco, ad basin atjusque orbis velut funicuius depingitur, 

 Lister, Hist. Conchy I. PL 508, Fig. 19. The shell there depicted is 

 evidently N. canrena ; but the Harwich fossil shell has a simple umbi- 

 licus, and not an umbilicus intersected by a callous process, as is the case 

 in N. canrena. This fossil seems more nearly to resemble N. glaucina, as 

 represented by Lister, PL 562, Fig. 9, of the same work. 



Among the most rare of the Blackdown fossils, is a Natica, approach- 

 ing in its character to N. canrena, Linn, and N. epiglottina, Lam. except 

 that the callosity lays in the contrary direction to what it does in those 

 species. The only one I know of was extricated from a mass of the 



