66 CLASS III. GASTEROPODA. ORDER VI. PULMOBRANCHIATA. 
This distribution, though clear, is certainly not well organized, for 
there is in reality a much stronger affinity between Helicarion and Heli- 
colimax (Vitrine), which are regarded as different genera, than between 
Cochlohydra (Succinea) and Helicigona (Carocolla), which are regarded as 
subgenera of one and the same genus; and again, Partula might have 
been considered as a subgenus of Helix with just as much propriety as 
Cochlogena (Bulimus); the genus Vertigo, moreover, proposed by Miiller, 
differs from the Pupe only in the animal having two tentacula. 
Perhaps there is no family throughout the system in which a more 
complete vein of aflinity may be traced than in that of the Colimacea ; 
we cannot therefore wonder at the many schemes that have been pro- 
posed to establish a definite form of classification. Gray divides his single 
family of Helicide into no less than forty-four genera; whilst Deshayes, 
at the same time, asserts that the Helices and Carocolle, the Pupe and 
Clausilia, the Bulimi, Partule and Achatine, should be severally united. 
But, as Nature will admit of no limitary line, it matters little whether we 
follow the first of these writers in setting the species out in tens, to every ten 
a name ; or the second, in setting them out in hundreds, to every hundred 
a name; so long as we adopt whichever method is really thought most 
subservient to memory and convenience. 
In the midst of these differences of opinion, we propose to divide the 
Colimacea into nine genera, distinguishing the Auriculacea and Cyclosto- 
maced, in imitation of Gray, as separate families. The former differ in 
being partially aquatic, and in their shells being always strongly plaited 
on the columella; the latter are terrestrial, but their shells are distin- 
guished by the rotundity of the aperture, and in being always operculated. 
The following are the genera into which this family is divided : 
He tix. BuLimus. 
CaRrocoLia. PaRTULA. 
ANOSTOMA. ACHATINA. 
Pupa. SucCINEA. 
CLAUSILIA. 
