62 



Natica, Lc 



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

 has a large foot, simijle tentacula 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 tlic side of the columella is covered with a calcareous, 

 thick, and convex layer |, 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 Nerila Jluviatilis, 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 

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

 Avhich ai'e 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- 



* Fovtlie species see the first div. of Gm. and Chemn., V, pi. clxxxvi — clxxxix. 



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

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



X Nerita perversa, Gm., a large fossil species ; Chemn., IX, cxiv, 975, 9/6. 



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



II Nerita pulKgera, Chemn., loc. cit., 1878 — 1879; — N. virginea, List., 604, 606. 



^ Nerita corona, Chemn., 1083, 1084. 



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

 irical Paracephulophora ; but they all appear to me to he diacious. 



