102 MOLLUSCA. 
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 Puysa. 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 Acuatina 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 Linneeus. 
To this genus we may refer the Buccinum acicula of Miller, 
which is found in England, and the Helix octona of Lin- 
neeus, erroneously considered as a native of Britain. 
22. VotuTA—This genus, as originally formed by Lin- 
neeus, depended, as he informs us, on the plice of the pillar, 
“ volute genus facillime distinguitur columella plicata.” 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 defined, “ Testa 
univalvis, ovata, subventricosa, apice papillari; basi emargi- 
nata. Columella plicata; plicis inferioribus, majoribus, vel 
longioribus.” The type of the genus is the voluta musica. 
Bruguiére removed from the Linnzean genus those species 
which are destitute of a groove at the base of their mouth, 
and of which Lamark formed the genera AurtcuLA, Tor- 
NATELLA, and VotvariaA. 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-mide and 
auris-jude 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 
