114 LAND AND FRESHWATER 
creasing, flatly convex above; aperture subvertical, broadly lunate, 
directed obliquely downwards from the columellar side ; columellar 
margin very oblique. 
Largest specimen :— 
Size: maj. diam. 28-0, min. 23-5; alt. axis 10-0, body-whorl 8°75 mm. 
= TQ), ssh WOON y V5; 0:40, 5 0-34 inch. 
This shell may be known from similar forms, even when young, 
by its more tumid and rounded form below, the rounded apex and 
shallow suture, and particularly the milky white colour of the 
interior of the aperture, which in adult shells often covers the 
columellar side of the body-whorl, also the strong band of colour 
bordering the peristome. 
Animal (Plate XXYV.). The right shell-lobe (.s.1., figs. 1, 2, and 8) 
is well developed and must be of considerable length when extended 
in life, for it is very long in the beautifully preserved specimens 
sent me by Mr. Ogle; the left shell-lobe overlaps the edge of the 
peristome as a simple band for its entire length (figs. 3, 4, and 8), 
and there is no tongue-like shell-lobe given off as in V/, indica 
(vide figs. 9 and 10, representing the mantle removed, and viewed 
from above and from beneath). The right dorsal lobe is as in M, 
indica, but the left is more decidedly divided into two portions 
(figs. 1, 3, and 4), the posterior being almost a separate lube by 
itself, and has that appearance when viewed from the exterior side, 
though the connexion is seen from below (vide fig. 8). The sole of 
the foot is divided into the usual central and side portions, and the 
segmental lines run quite across it from side to side. 
The pedal line is particularly well defined by two parallel grooves, 
enclosing a series (as in all these forms) of oblong epidermal spaces. 
On reaching the large elongate labial tubercle, situated on either 
side below the mouth, this pedal line is continued diagonally back- 
wards and follows a distinct deep groove, which leads up to the 
posterior upper part of the neck underneath the mantle-lobes. A 
row of tubercles also starting from the above labial tubercle borders 
this groove on its upper margin, and thus distinctly divides the 
prosoma with the mouth, tentacles, and generative apparatus from 
the muscular foot, and would correspond to the more distinct ros- 
trum-like head of some species of Cyclophoride &c, (figs. 4 and 5). 
Along this groove the mucous fluid as it is secreted no doubt would 
be carried and thence beneath the mantle completely over the dorsal 
part of the animal, thence down the lateral grooves, meeting the 
flow of the same fluid at their junction with the pedal line, to 
be eventually thrown off at the extremity. Mr. J. Wood-Mason, in 
a paper published in the P. A. 8. B. March 1882, enters into the 
question of this pedal groove (his peripheral groove), and was the 
first to define its use. He does not appear to have considered this 
oblique groove, which would so much more completely spread the 
lubricating fluid over every part of the animal, and without the 
exclusive aid of the ciliated surface; however, this groove is not so 
distinctly seen in most other species. 
