VITRINA PELLUCIDA. o 
Description. —ANIMAL light-grey, HEAD and TENTACLES blackish ; the faintly- 
spotted MANTLE is partially external, projecting in front of the shell, and placed 
on the dorsum of the animal, asin Limax; it is also reflected over the margin of 
the shell anteriorly, and is in addition furnished with a linguiform lobe on the right 
side, which extends partially over the apex of the shell; the TENTACLES are short 
and stout, with eye specks at the summits of the posterior pair ; FOOT rather narrow, 
SOLE trifasciate, median area pale, darker marginally and at the caudal extremity, 
which is attenuated and prolonged beyond the margin of the shell; RESPIRATORY 
ORIFICE on right side of body and margined with black ; REPRODUCTORY ORIFICE 
near middle of neck ; EPIPHRAGM very thin, membranaceous, and transparent. ‘The 
animal is very large, relatively to its shell, into which, however, it can ordinarily 
wholly withdraw the body, but if the tissues are saturated with moisture, no 
amount of irritation or force can compel its entire concealment. 
SHELL subglobose ; WHORLS 3—4, somewhat convex above, and rather flattened 
below, very thin, fragile, and transparent, sometimes with a yellowish or greenish 
tinge, changing to a dull whitish opacity in dead shells, which have laid exposed to 
the weather; there are a few indistinet lines of growth, and some exceedingly 
delicate spiral striation ; SPIRE small, not prominent, and terminating in a blunt 
apex ; BODY-WHORL large, voluminous, and somewhat oblique ; SUPURE shallow, 
with minute strize or puckerings, and showing a narrow bordering ; APERTURE 
somewhat oval, but encroached upon by the penultimate whorl; MARGINS simple, 
sometimes faintly pigmented, and at times slightly reflected around the slightly 
concave but imperforate umbilical region, where a delicate apertural film is some- 
times present. 
When containing the retracted animal, the shell appears of a chocolate-brown 
colour above, becoming blackish towards the aperture ; on the underside, the pen- 
ultimate whorl is of a paler chocolate-brown, and shows the whitish subtriangular 
renal organ about one-fourth of a revolution from the aperture, bordered outwardly 
at a little distance by an obliquely transverse black line. 
Length, 7 mill. ; width, 5 mill. ; altitude, 4 mill.; and the average weight of an 
adult shell is about ,'th of a grain. 
INTERNALLY, the constituent ganglia and commissures of the o-sophageal NERVE- 
RING are distinctly defined, and the abdominal ganglion adjoins the right pallial 
ganglion on the visceral loop ; while the ‘‘ organ of Semper”! has not been detected. 
The SUPRA-PEDAL GLAND is well developed and rather compact, occupying four- 
fifths of the length of the foot, and deeply imbedded in the tissues; the anterior 
part is enveloped by glandular cells, and the longitudinal folds and groove are well 
marked, but there is no fold on the roof; an important blood sinus accompanies 
the gland and is in parts adherent to it. 
The CEPHALIC RETRACTORS are of the usual type, the main or central branch 
being affixed to the pharynx and giving off early in its course the lateral muscles to 
the OMMATOPHORES, from which arise the smaller subsidiary muscles to each of the 
lower TENTACLES. 
The REPRODUCTIVE ORGANS are in our species simple and uncomplicated. The 
OVOTESTIS is pale in colour, imbedded in the substance of the LIVER or DIGESTIVE 
GLAND, and connected with the base of the ALBUMEN 
GLAND by a sinuate HERMAPHRODITE DUCT; the 
VAS DEFERENS soon after leaving the conjoined ducts 
is bent upon itself and also runs parallel with and 
close to the penis sheath, to which it is closely bound 
by a thin museular sheath; the PENIS SHEATH is 
apparently formed by a simple thickening of the vas 
deferens, but its lumen is not central, being nearer the 
outer wall, and distally is of a glandular structure, 
separable into an upper and a lower portion, the Fic. 4.—Proximal end _of 
vas deferens entering at the point of junction; the — Reproductive organs of /’st7(ua 
5 5 : pellucida X 4 (after Simroth). 
upper glandular section and one-sided swelling cannot 
be explained as a flagellum, as the retractor is affixed at that point; the PENIS 
SHEATH, the short smooth FREE OVIDUCT, and the globular SPERMATHECA with 
its short neck and bulbous base open almost together into the ample vestibule. 
The ALIMENTARY CANAL is of the usual triodromous® type, consisting of an 
INGESTIVE TRACT, at the termination of which is the STOMACH ; this is succeeded by 
a couple of INTESTINAL COILS and a RECTAL or excretory section, which opens out- 
wardly close by the respiratory aperture. 
1 Monog. i., p. 185. 2 Monog. i., p. 284. 
