84 CLASS III. GASTEROPODA. ORDER VI. PULMOBRANCHIATA. 
ACHATINA, Lamarck. 
Testa ovata vel oblonga, epidermide sepissimé induta; spira plus mi- 
nusve elevata; apertura integra, longitudinali, rard suborbiculari, 
labro tenui, acuto, nunquam reflexo; columella levi, basi trun- 
cata. 
The Achatine were assigned by Linneus to his genus Bulla ; and Bru- 
guiére referred them to a place amongst his Bulimi; but although in- 
cluded with this extensive and miscellaneous series, they were still asso- 
ciated together, on account of the truncature of the columella ; thus anti- 
cipating in a manner the genus which Lamarck subsequently proposed 
with the above title. The truncature of the columella is not, how- 
ever, the only character which serves to distinguish the Achatine from 
the Bulimi; the margin of the aperture is invariably simple, never thick- 
ened or reflected, and a difference of habit communicates a peculiarity of 
appearance to the shell, by which they may always be recognised. The 
Bulimi are inhabitants of a dry soil, and live either upon the branches 
of trees, or clustering at the roots under the decayed and fallen leaves: 
the Achatinz, on the contrary, require moisture, and are found located 
near wet and marshy places, in the vicinity of ponds or rivers. Still, as 
we are of course presented with all the intermediate modifications of these 
characters, nature again opposes herself to the arbitrary rules of classi- 
fication ; and whilst some authors have thought of diminishing the num- 
ber of genera, others have laboured to increase it. Deshayes proposes 
to return the Achatine to the genus Bulimus ; and the same arrange- 
ment is followed by Ocken, under a new title, Pythia. De Montford, on 
the contrary, has instituted two new genera out of the one under consi- 
deration ; Liguus, from the Achatina virginea ; and Polyphemus, from the 
Achatina glans. 
