74 EOCENE MOLLUSCA. 
smooth, inflected and truncated at its base, forming a slight notch where it joins the 
outer lip. 
The third division made by Bruguiere in his genus Bulimus, consisting of those 
species in which the columella is truncated at the base, was formed by Lamarck 
into the present genus. From this Montfort withdrew his genera Liguus, (Chersina, 
Humph.,) consisting of the conical forms in which the aperture is short and nearly 
round; and Polyphemus, comprising the oblong sub-turreted species, with an un- 
dulating outer lip, to which Bolten had already given the name Oleacina, and which 
forms the genus Glandina of Schumacher and Say, and the sub-genus Cochlicopa of 
Feérussac. 
As some of the Bulimi present a sharp outer lip, the truncation of the columella 
appears to be the only character by which the Achatinz can be separated from that 
genus, and the value of this character must depend on its being the result of some 
peculiarity of generic importance in the organisation of the animal. M. De Blainville 
states that he has observed in the animal of Achatina zebra an interruption in the collar 
where the two sides unite, as if caused by the exsertion (saillie) of the columellar 
muscle, and to this he attributes the truncation of the columella; but, according to 
Ferussac, this truncation is not the result of any peculiar organisation, as is the case 
in other molluscous animals, the columella of whose shells present this character; and 
that author therefore unites the Achatine to his genus Helix, of which they form the 
sub-genus Cochlitoma; and M. Deshayes, on account of the similarity of organisation 
presented by the animals of Bulimus and Achatina, proposes to re-unite Achatina 
with Bulimus. The genus, however, is very generally adopted as well by English as 
by foreign Malacologists, and I have therefore retained it. 
The subdivisions proposed by Bolten and Montfort depend on the proportions 
and other characters in the shell, of trifling importance, which are generally considered 
as insufficient for generic distinction, however useful they may be for the division of 
a genus into sections. The recent species 4. glans, and the cognate species which 
form the genus G/andina, are confined to the West Indian Islands, and the adjacent 
parts of the American Continent; and the peculiar form of the outer lip may be 
used with convenience, as one of the indications of the limits of geographical dis- 
tribution of species. 
The Achatinz are generally large shells; some, in fact, attain a greater size than 
any other land shells at present known, and many are covered with an epidermis. 
Although generally dextral, they are in some species constantly sinistral. They are 
found chiefly in tropical climates, and, according to Blainville,in marshy lands. Some 
few are European, but only one or two small species occur in England. One fossil 
species (4. pellucida) has been described by M. Deshayes from Parnes; and Bouillett, 
in his catalogue of the fossil shells of Auvergne, has given another species, which he 
refers to the recent 4. acicula (Lamarck). 
