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. mhcarinatm. 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 striae 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.) 

 Uber. Humph. 1797. 



LUNATUS. Id. 



NATicrs. Montf. 1810. 



POLINICES. Id. 



Mammilla. Schum. 1817. 

 Nacca. Risso. 1826. 

 Nevekita. Id. 

 Ampullaria. Flem. 1828. 

 Globulus. /. Sow. 1834. 

 BuLBUS. Brown. 1838. 

 Globularia. Swains. 1840. 

 Mammillakia. Id. 



Pachylabra. Id. 



Naticina. Guild. 1840. 

 Naticella. Id. 



Cernina. Gray, 1840. 

 Amauea. Mailer, 1842. 

 Naticopsis. M'Coy. 

 Deshayesia. Raulin, 1844. 



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

 with fine striae, 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 umbi- 

 licus ; 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 ' Malaco- 

 logia Monensis' (1838, p. 62), reports that the animals of two calcareous operculated 

 Naticae, obtained at Algiers, exactly agreed in generic character with the British 

 corneous operculated species ; and M. Philippi examined the animals of species 



