two Genera of Molluscous Animals. 31 



Tesfa hcvis, (epidermicle tenui caduca,) Naticcv similis, longitudinaliter plica- 

 tula, anfractu basilar! subit^ valdfe incrassato, reliquis minutis. 



Umbilicus quasi semiclausus : in adultis callositate effusa nonnunqukm omnin6 

 clausus. 



Columellce calloscc basis, vix a columellario depressione transversa parvula di- 

 stinguenda : fossula ejus antica saepiiis lata. 



* umbilico clauso. N. Mammilla, Lam. 

 ** VMibilico aperto. N. lactea, Guild. 



Typus. Naticina lactea. 



N. tota flavescente-lactea, capite rufescente, abdomine nigrescente-flavido, 



operculo castaneo margine diaphano. 

 Testa ovalis, ventricosa, lactea, nitida, spira prominula, anfractibus septem 



epidermide fuscescente-ferruginea tectis, apicalibus nudis minutis. 

 Nerita Mammilla, var. C. Dillwyn Cat. vol. ii. p. 985. Lister Conch, tab. 371. 



/.22? 

 Habitat in profundis Oceani Caribsei frequens, nee cum Neritis littora petens. 



Axis 1-iV unc. — Diam. j-j 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 Xatica seems to me imperfect. The eyes it is said to possess are either 

 wanting in Naticina, 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 A", mammillaris. Lam., the var, B. of Dillwyn, which occurs 

 in these seas. 



Dentalium. 



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 



