GASTEROPODA. 



205 



Atlanta. Lesueur. (Steira Esch.) — Shell compressed, 

 somewhat resembling Carinaria ; having the apex spirally 

 whorled, and a sharp keel ; trans- 

 parent, and large enough to con- 

 tain the animal ; operculum thin, 

 horny, and spiral. Animal, the 

 head distinct, more or less 

 lengthened, having large eyes, 

 and before them a pair of long 

 tentacula ; the mouth is pro- 



x Atlanta. 



boscis-formed, more or less 



pliable ; the foot has a compressed fin ; and there is a 

 prolongation behind, which bears a horny operculum. — 

 2 species. 



The species A. Peronii is found in the seas of hot 

 climates, and is a minute shell of great beauty. 



Oxygyrus. Benson. (Ladas Cantr. : Helicophlegma 

 D'Orb.; Brownia U Orb.) — Shell wheel-shaped, rolled 

 up, with encompassing whorls, very similar to Belleroplion, 

 the next genus, which is only fossil. Animal differing 

 from Atlanta in having, instead of tentacula, a naked fold 

 of the skin. — 2 species. 



O. Keraudreni is found in the Atlantic and Mediter- 

 ranean Sea, and is the best known. 



Bellerophon. Montf. — Shell convolute, symmetrical, 

 umbilicated, with a double dorsal ridge; aperture wide, 



Bellerophon. 



