132 UNIVALVES. — NERITA. 



NERITA.— Nerite or Hoof-Shell. 



Animal — a Limax : Shell univalve, spiral, gibbons, flattish 

 at bottom; aperture semiorbicular or semilunar; pillar- 

 Up transversely truncate, Jlattish. 



THIS genus contains only sixty-seven species, and but 

 few of any great beauty or rarity. 



There is considerable variation in the form and mark- 

 ings of the Neritge: some are spiral, with prominent whirls; 

 others have their whirls partly or wholly concealed ; some, 

 again, are umbilicated, while others are perfectly entire 

 and solid; and many have the umbilicus partially covered 

 by a repand lip, or fissurated nodule. 



The interior of the mouth and lips is, in many species, 

 toothless; but, in others, both lips are beset with strong 

 prominent and articulated teeth, often terminating in dis- 

 jointed, elevated striae, or protuberant granulations. 



In most species, the back of the shell is covered with 

 strong, elevated ribs, sometimes nodulous and imbricated; 

 it is often only minutely striated, and has frequently a 

 perfectly smooth surface and brilliant polish. 



Of the umbihcated species may be particularized the N. 

 canrena, of which there are many beautiful varieties ; and 

 the N. cancellata, N. glaucina, N. vitellus, and N. mammil- 

 la ; the common variety of the latter shell is white, having 

 a porcelain appearance; but the rarer varieties incline to a 

 brownish orange, having their lips surmounted with a black 

 margin or border. The N. fulminea is marked with an- 

 gular stripes, resembling forked lightning. 



The next division of the Nerites consists of those which 

 are imperforated and toothless, as the N. corona and N. 

 liuviatilis ; the former is often of a blackish colour, and has 



