ARIONID^. 227 



and their shells are very thin, and are usually confounded 

 with those of Vitrina. 



Species of Helicarion. 



Cuvieri, Ferns. nigra, Quoy and Gaim. 



flammulata, Quo;/ and Gaim. robusta, Gould. 



Freycineti, Ferns. scorpio, Gould . 



marcida, Gould. viridis, Quoy and Gaim. 



Fain. AEIONIDiE. 



Lingual teeth numerous, uniform, close together. Animal 

 elongate, limaciform ; body not distinct from the foot. Eye- 

 peduncles and tentacles retractile under the skin. Mantle 

 shield-like, on the fore part of the back ; respiratory orifice 

 on the right side. Foot with the caudal extremity rounded, 

 somewhat truncated, with a mucous gland at the end. 



Shell internal, rudimentary. 



Genus ARION, Ferussac. 



Animal limaciform. Tentacles and eye-peduncles mode- 

 rate. Mantle shield-like, on the fore part of the body ; ori- 

 fice of respiratory sac at the right anterior border ; repro- 

 ductive aperture immediately below it. Tail rounded, trun- 

 cate, and furnished with a terminal mucous pore. 



Shell internal, in the form of an irregular mass of calca- 

 reous granules. 



Syn. Limacia, Hartm. Limacelia, Brard. 



Ex. A. ater, Linnaus, pi. 80, fig. 3. 



This genus differs from Geomalacus in the position of the 

 reproductive orifice, which is immediately below the respi- 



