LAND SNAILS. 
169 
all round, more or less reflected, and whitish.; it 
varies in form, being ovate, oblong, or subquad¬ 
rate; the internal plaits are usually three in 
number, and all situated on the pillar. The 
clausium is curved, thin, with a thick revolute 
smooth margin. The dental formula is 201 - 2 —. 
O 9 0 
The animal is very slender and elongated, and 
drags its shell in the same line as the foot and 
neck (see PL IX., fig. 14) ; for it is incapable 
of raising it, unless when about to repose, when 
the shell is inclined at an angle of about 70°. 
A marked and persistent variety, 0. dubia 
(PL IX., fig. 92), is characterized by its larger 
size and more spindle-shaped form; it is only 
recorded from the counties of York, Durham, and 
X orthumb erland. 
Clausilia Rolphii (PL IX., fig. 93).— This 
species was named by Dr. Gray after Mr. Rolph, 
an English conchologist. It is easily distinguished 
from the other species of the genus by its more 
spindle-shaped shell, and in the presence of four 
or five folds, two of which are longer than the 
rest, within the aperture. The shell is half an 
inch to three-fifths in length, and one-seventh 
to one-eighth in breadth, of a slightly glossy red¬ 
dish-brown, with regular transverse striations; 
there are ten and a half whorls; the aperture 
is subquadrate sinuous on the outer side; the 
margin is thick, white, and detached all round. 
