LAND SNAILS. 
171 
a fulvous tint rather than the purplish hue which 
pervades the latter; 0 . Mortilleti has fewer 
teeth. 
Genus Achatina (Agate Shells ). 
The shells of this genus are elongated, cylin¬ 
drical, thin, glossy, and smooth; the aperture is 
oval, and the outer lip thin and not reflected; the 
columella is twisted and truncated in front, that 
is, appearing as if cut off below. The species 
are very numerous, being about 150 in number, 
and especially inhabit tropical and subtropical 
forests and wastes. The majority of the agate 
shells are beautifully coloured. 
The genus is represented by A. costellata in 
the Upper Eocene deposits of Bembridge, Isle of 
Wight. 
The great African species are among the 
largest of the land mollusca, and attain a 
length of eight inches. The only British 
species is— 
Achatina acicula —{the Needle Agate Shell) 
(PI. IX., fig. 89)—and is a perfect Lilliputian 
among the snails with which it is generically 
allied; a pill-box, that may be carried in one's 
waistcoat pocket, is amply capacious for many of 
these pigmies, which rarely exceed one-sixth of 
an inch in length; whereas a collector among 
