ATLANTA. 9 1 



lanthinida, at the bottom of the respiratory cavity of the 

 mantle ; the orifice of the reproductive organs is at the right 

 side in front of the vent. As M. Morch has pointed out, 

 the general form of the animal and structure of the foot is 

 very similar to that of Onustidee, which, however, inhabit 

 the bed o( the sea, and never approach the surface like the 

 Heteropods. The lingual dentition is similar to that of 

 the Pterotracheida. 



Genus ATLANTA, Lesueur. 



Operculum ovate, sub -spiral, lamellar, nucleus apical, 

 dextrally spiral. 



Shell spiral, compressed, glassy, transparent, conspi- 

 cuously keeled; spire flattened, nucleus dextrally spiral, 

 smooth ; aperture oval, narrow, fissured in front at the keel. 



8yn. Steira, Eschscholtz. 



Ex. A. Peronii, Lesueur and Blainvitte, pi. 69, fig. 5. 

 Operculum, A. Peronii, fig. 5, a. Shell, A. Peronii, fig. 5, b. 



The Atalants, which were first discovered by Lamanon, 

 one of the Naturalists attached to the Expedition of La Pe- 

 rouse, are beautiful and sprightly little creatures, when ob- 

 served in their native element, swimming rapidly about, and 

 examining every object within their reach with their long, 

 muzzle-shaped heads. The shells are transparent and glassy, 

 and may be considered the existing analogues of the fossil 

 Bellei'ophon and Porcellia; about fifteen species have 

 already been described. 



Species of Atlanta. 



brunnea, Eyd. Gaudichaudi, Eyd. 



cunicula, Gould. heliconoidca, Eyd. 



depressa, Eyd. inclinata, Eyd. 



