62 



3IOLLUSCA. 



NATICA, Lam. 



Neritop with an umbilicated shell; the animal of the species known 

 has a large foot, simple tcntacula with the eyes at their base, and a 

 horny operculum*. 



NERITA, Lam. PELORONTA, Oken. 



The umbilicus wanting; shell thick, columella dentated, and oper- 

 culum stony ; the eyes of the animal on pedicles by the side of the 

 tentacula, and a moderate foot f . The 



VELATA, Montf. 



Where the side of the columella is covered with a calcareous, 

 thick, and convex layer J, is distinguished from it, but perhaps 

 without any good reason ; also the 



NERITINA, Lam. 



Where the shell has no umbilicus and is thin, with a horny oper- 

 culum ; the animal is like a true Nerita, and most generally the 

 columella is not dentated. It inhabits fresh water. 



A small species, very prettily coloured, abounds in the rivers 

 of France ; it is the Nerita fluviatilis, L. ; Chemn., IX, cxxiv, 

 188 . 



The columella in others, however, is finely crenulated ||, and of 

 this number there are some in which the spire is armed with long 

 spines CLITHON, Mont.^ 



FAMILY II. 

 CAPULOIDA**. 



Recent researches have convinced us that it is to the Trochoida that 

 we must approximate this family, which contains five genera, four of 

 which are taken from the Patellae. They all have a widely opened, 

 scarcely turbinated, shell, with neither operculum, emargination, nor 

 siphon; the animal resembles the other Pectinibranchiata, and has the 

 sexes separate. There is but one branchial comb transversely ar- 



* For the species sec the first div. of Gm. and Chemn., V, pi. clxxrvi clxxxix. 



t For the species see the third div. of Gm. and Chemn., V, pi. cxc cxciii, 

 and Sowerby, Gen. of Sh., No. XV. 



J Nerita potcrsa, Gm., a large fossil species ; Chemn., IX, cxiv, 975, 976. 



Add, Nerita turrita, Chemn., IX, cxxiv, 1085. 



|| Nerita pulUgera, Chemn., loc. cit., 1878 1879; N. virginea, List., 604, 606. 



^ Nerita corona, Chemn., 1083, 1084. 



** M. de Blainville places most of them among his hermaphroditical, non-symme- 

 trical Paracephalophora ; but they all appear to me to be edacious. 



