140 MOLLUSCA FROM THE CRAG. 



This elegant little shell is not particularly rare. My first specimens were more 

 or less injured at the aperture, and the possession of some, obtained recently, have 

 the peritreme perfectly entire, showing a deeply sinuated form of aperture, like 

 that of A. subcarinatus. I have, therefore, placed it among its probable relations. 



The apex is somewhat obtuse, and the suture deep, with an incipient canal at 

 the junction of the outer lip with the body whorl, where it joins, as nearly as 

 possible, in the centre of the volution. The stride are rather coarse, and more 

 distant upon the base of the shell than they are upon the upper part, and the lip is 

 slightly sinuated at the outer or lower angle of the aperture. 



Natica, Adanson, 1757. 



Ruma (spec). Chem. (fide Gray.) 

 Ubeb. Humph. 1/97. 

 Lunatus. Id. 

 Naticus. Mont/. 1810. 



POLINICES. Id. 



Mammilla. Schum. 1817. 

 Nacca. Risso. 1826. 

 Neverita. Id. 

 Ampullaria. Flem. 1828. 

 Globulus. J. Sow. 1834. 

 Bulbus. Brown. 1838. 

 Globularia. Swains. 1840. 

 Mammillaria. Id. 



Pachylabra. Id. 



Naticina. Guild. 1840. 

 Naticella. Id. 



Cernina. Gray, 1840. 

 Amaura. Mailer, 1842. 

 Naticopsis. M'Coy. 

 Deshayesia. Raulin, 1844. 



Gen. Char. Shell generally thick, strong, smooth, and glossy, occasionally 

 covered with fine stria?, of an ovate, globulous, or subspheroidal form, with a short 

 or slightly elevated spire ; aperture oval, or semilunate; outer lip plain and simple; 

 inner lip sometimes depositing a callosity, the callus modifying the form and size 

 of the umbilicus ; operculum corneous or calcareous. 



This is at present by no means a well-defined genus ; several species have been 

 separated, in consequence of an extended form of the inner lip, by which the 

 umbilicus is closed, while some naturalists have considered the distinction of a 

 corneous from a calcareous operculum sufficient to justify generic separation. The 

 author of ' Malacologia Monensis ' (1838, p. 62), reports that the animals of two 

 calcareous operculated Naticse, obtained at Algiers, exactly agreed in generic 

 character with the British corneous operculated species ; and M. Philippi examined 



