26 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 
The foot is bilobed anteriorly, and its front margin is duplicated. 
It bears a conspicuous pedal pore on the sole at about its middle. 
The opercular pad is large. The s¢phon is very short, and the edge of 
the mantle is continued round its base as a very slight and incon- 
spicuous collar. Martin F. Woodward has stated that the siphon is 
devoid of appendages: my specimen, however, showed a prominent 
tongue-shaped outgrowth of the left border of the siphon at its base, 
and I have since made out the existence of a similar structure in 
Woodward's specimen, in which its presence had been obscured by 
coagulated mucus. ‘The posterior siphon is represented by but a slight 
groove. 
The animal appeared to have been entirely destitute of colour- 
markings. The eye-spots are red in the preserved specimen. 
Introvert.—The rhynchostome, or external opening of the introvert- 
sheath, is rounded and quite simple. The eversible portion of the 
introvert is conical in form, somewhat flattened dorso-ventrally, and 
with the base of the cone, not at right angles to its axis, but 
facing downwards. Its walls are enormously thickened and muscular, 
especially at its base. The musculature of the introvert consists of 
two lateral series of rounded bundles arising on the body-wall, and 
inserted at close intervals along the sides of the introvert-sheath 
(Fig. 6). These bundles become more developed towards the base of 
the introvert, which is further provided with a powerful retractor, 
arising on the roof of the body-cayity and inserted dorsally on to the 
introvert-sheath. 
Alimentary Canal.—The mouth is a small vertical slit at the extreme 
end of the proboscis: it is destitute of jaws and unsupported by 
cartilage. The buccal mass is well developed, measuring about 9 mm. 
in length. Its roof is extremely thin and transparent, and so closely 
applied to the csophagus as to give the buccal mass a crescentic 
transverse section. The initial segment of the cesophagus is perfectly 
straight, and practically buried up in the muscular root of the imtro- 
vert. After passing out of the introvert the cesophagus becomes 
somewhat enlarged and very thick-walled. In the contracted condition 
it passes sharply forward, to the right of the retracted introvert, as far 
as the nerve-ring. Passing through this, it makes another sharp turn 
backwards, and appears to be continued without any break as Leiblein’s 
gland; the oesophagus appearing to come off below, immediately 
behind the nerve-ring, as a a thin- walled, and compa -atively insig- 
nificant, outgrowth of what is in reality its own diverticulum. The 
explanation of this apparent anomaly would seem to be that here, as 
in perhaps the majority of instances, the point of separation of the 
cesophageal diverticulum from the cesophagus is not its true point of 
origin, the latter being situated far forward in advance of the nerve- 
collar, né mely, at the point of apparent thickening of the cesophagus. 
From here, backwards, the cesophagus is so closely bound up with its 
diverticulum as to be indistinguishable from it by ordinary dissection. 
After the separation off of Leiblein’s gland the cesophagus undergoes 
no further convolution; but its walls soon become so exceedingly thin 
