PACE: ANATOMY OF VOLUTA MUSICA, LINN., ETC. 20 
where it is greatly thickened to form a definite posterior siphon, which 
shows slight pigmentation and is supported on cartilage. The mantle- 
edge is thin and unpigmented. In the contracted state, the penis is 
hatchet-shaped and directed backwards ; it les entirely under cover 
of the mantle. 
Pallial Complex.—The condition of the organs of the pallial complex 
presents no unusual features. The bipectinate osphradium is highly 
developed, and its folie are darkly pigmented. The laminz of the 
ctenidium are triangular in shape and unpigmented. The hypobranchial 
gland is well developed. Its secretion was at first (as preserved in 
formol) of a rich purple colour, but this changed to a vivid green 
under the action of fresh water. 
Introvert.—The introvert is of comparatively large size and almost 
completely eversible. In this condition (Fig. 1) it appears as an 
elongated structure, which is flattened dorso-ventrally and slightly 
curved upwards. Attention has already been directed to the pigmen- 
tation of the outer surface of the introvert. In the retracted state 
it les entirely within the body-cavity, passing to the right side over 
the cesophagus, and forming a curved lenticular mass which occupies 
the greater part of the anterior region of the body-cavity and lies 
transversely to the long axis of the body. 
The musculature of the introvert is not greatly developed; it 
consists mainly of a series of strands inserted along the greater 
curvature of the introvert-sheath. 
Alimentary Canal.—The mouth appears as a conspicuous vertical 
slit at the extreme end of the everted introvert. It appears to be 
supported by a couple of small masses of cartilage. The cesophagus, 
in the everted condition of the introvert, passed straight back, 
without any convolution, from the mouth to the stomach; and it 
appeared to be of pretty uniform calibre throughout the whole extent 
of its course. When the introvert is retracted, the cesophagus, after 
emerging from the introvert, passes sharply forward underneath the 
latter and to the right side, as far as the nerve-collar, where it makes 
another sudden bend and resumes its backward direction. 
Leiblein’s Gland. — There is a greatly developed cesophageal 
diverticulum, forming a very prominent mass lying dorsad to the 
cesophagus (Fig. 2). It is a very stout, much convoluted, tubular 
structure, of large calibre, larger than that of the cesophagus, arising 
immediately behind the nerve-ring, and terminating in a but slightly 
enlarged, thick-walled, spheroidal sac. Its convolutions are bound 
up in exceedingly tough and closely adherent connective tissue; and 
they present a very characteristic glistening appearance. In colour 
the terminal segment of the cesophageal cecum is pure white and 
somewhat translucid, while its duct is yellowish and opaque. The 
enlarged terminal segment is closely bound up. with the cesophagus ; 
but its lumen is certainly not in actual communication with that of 
the gut at this point. 
Salivary Glands. — As probably obtains in the majority of the 
higher Prosobranchiata, two pairs of so-called salivary glands are 
represented ; and both pairs lie entirely in front of the nerve-collar. 
