62 
MOLLUSCA. 
Natica, Lam. 
Neritae with an umbilicated shell ; the animal of the species known 
has a large foot, simple tentacula with the eyes at their base, and a 
horny operculum* * * § . 
Nerita, Lam. — Peloronta, Ohen. 
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, Latn. 
AVhere 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 Jluviafilis, L. ; Chemn., IX, cxxiv, 
188 §. 
The columella in others, however, is finely crenulated ||, and of 
this number thei’e are some in which the spire is armed with long 
spines — Clithon, Afont.^ 
FAIVIILY 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 Patellm, 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 hut one branchial comb transversely ar- 
* Fov tlie species see the first div. of Gm. and Chemn., V, pi. clxxx-vi — clxxxix. 
For the species see the third div. of Gm. and Chemn., Y, pi. cxc — cxciii, 
and Sowerhy, Gen. of Sh., No. XV. 
J Nerita perversa, Gm., a large fossil species ; Chemn., IX, cxiv, 975, 9/6. 
§ Add, Nerita turrita, Chemn., IX, cxxiv, 1085. 
II Nerita putt igera, Chemn., loc. cit., 1878 — 1879; — N. virginea, List., 604, 606. 
^ Nerita corona, Chemn., 1083, 1084. 
** M. de Rlainville places most of them among his hermagjliroditical, non-symme- 
trical Paracephalophora ; bnt they all appear to me to be dicecious. 
