102 MOLLUSC A. 



form a distinct genus next the bulinius. The B. fontinalis, 

 hypnorum, and rivalis, reside in fresh water. They have, 

 with much propriety, been formed into a distinct genus by 

 Draparnaud, which he calls PHYSA. They are all sinistral 

 shells, and will require further division when the form of the 

 animal shall become the basis of generic distinction. The 

 fontinalis and hypnorum are natives of Britain. 



In the genus ACHATINA of Lamark, the pillar is trun- 

 cated as in the terrebellum, but the base of the mouth is 

 entire. It is represented by the bulla achatina of Linnseus. 

 To this genus we may refer theSuccinum acicula of Miiller, 

 which is found in England, and the Helix octona of Lin- 

 naeus, erroneously considered as a native of Britain. 



22. VOLUTA. This genus, as originally formed by Lin- 

 naeus, depended, as he informs us, on the plicae of the pillar, 

 " volutae genus facillime distinguitur columella piicata." But 

 as this character belongs to many shells otherwise very dif- 

 ferent in form, succeeding conchologists have separated 

 many species from the genus, and reduced it within more 

 natural limits. As it now stands it is thus denned, " Testa 

 univalvis, ovata, subventricosa, apice papillari ; basi emargi- 

 nata. Columella piicata ; plicis inferioribus, majoribus, vel 

 longioribus." The type of the genus is the voluta musica. 



Bruguiere removed from the Linnaean genus those species 

 which are destitute of a groove at the base of their mouth, 

 and of which Lamark formed the genera AURICULA, TOK- 

 NATELLA, and VOLVARIA. In the latter the spire is not 

 produced ; in the former it is produced. To the genus au- 

 ricula, which contains land-shells, the V. auris-midce and 

 auris-judce belong. The V. tornatilis is the type of the 

 genus tornatella. In his reference to the genus volvaria, 

 Lamark quotes the bulla cylindracea of Pennant and Da 



