two Genera of Molluscous Animals. 3l 
Testa levis, (epidermide tenui caduci,) Natice similis, longitudinaliter plica- 
tula, anfractu basilari subitó valdé incrassato, reliquis minutis. 
Umbilicus quasi semiclausus : in adultis callositate effusá nonnunquàm omnind 
clausus. 
Columelle callosæ basis, vix à columellario depressione transversá parvulâ di- 
stinguenda: fossula ejus antica szepiüs lata. : 
* umbilico clauso. N. Mammilla, Lam. 
** umbilico aperto. N. lactea, Guild. 
Typus. JVaticina lactea. 
N. tota flavescente-lactea, capite rufescente, abdomine nigrescente-flavido, 
operculo castaneo margine diaphano. 
Testa ovalis, ventricosa, lactea, nitida, spirà prominulà, anfractibus septem 
epidermide fuscescente-ferruginea tectis, apicalibus nudis minutis. 
Nerita Mammilla, var. C. Dillwyn Cat. vol. ii. p. 985. Lister Conch. tab. 571. 
f. 22? 
Habitat in profundis Oceani Caribæi frequens, nec cum JVeritis littora petens. 
Axis 14*- unc.—Diam. ++ unc. 
It is commonly found in all collections of West Indian shells, though the epi- 
dermis and operculum are rarely preserved. Lamarck's description of the ani- 
~ mal of Natica seems to me imperfect. ‘The eyes it is said to possess are either 
wanting in JVaticina, or escape observation from their paleness. Mr. Gray, the 
zealous author of the Spicilegia Zoologica, has with great judgement pointed 
out the affinity of Sigaretus to Natica. Its proper place in the family I shall 
explain hereafter. 
The shell before us is very different from the Asiatic N. Mammilla of La- 
marck, and the JV. mammillaris, Lam., the var. B. of Dillwyn, which occurs 
in these seas. 
DEnNTALIUM. 
The nature and proper station of Dentalium were involved in much con- 
fusion till the observations of M. Deshayes were made known to us. A trans- 
lation of his interesting memoir is given in the Zoological Journal, and is of 
great value to the student. The specimens which this naturalist examined 
