48 HYALINIA HELVETICA. 
o 
lead colour, due in part to the dark RETRACTORS, which show as a gradually paling 
line at each side of the back; lower tentacles pale grey, and about 1 mill. in length. 
Mucus thin and almost colourless. 
SHELL somewhat convex above and rather com- 
pressed beneath, very smooth, semitransparent and 
glossy, with faint and shallow transverse striation, 
most prominent at the suture; of an amber-brown 
colour above, paling beneath into a whitish area 
around the UMBILICUS, which is narrow and deep ; oe : 
WHORLS 5-6, convex, increasing regularly, spire Se oper rhroueyy ne 
slightly elevated ; SUTURE distinct ; APERTURE shape and character of the whorls 
crescentic, slightly oblique; PERISTOME thin and and umbilical cavity, x 4 (froma 
sharp. preparation by Mr. F. Rhodes). 
When the animal is withdrawn into the shell, the upper side appears of a dark 
yellowish-brown, darker towards the apex, and showing near the mouth of the shell 
a black margin to the edge of the mantle, 15 to 2 mill. in width; the under-side is 
dark brown up to the triangular and dark renal organ, beyond which the body is 
blackish in parts with the black margin to the mantle, as on the upper side. 
Diam., maj. 8 mill. ; min. 7 mill. Alt. 4 mill. Average weight of the adult 
shell about 2ths of a grain. 
The ALIMENTARY CANAL is scarcely distinguishable from that of its allies, and 
is of the usual triodromous character, 
with its first anterior flexure held in 
place by the CEPHALIC AORTA; the 
SALIVARY GLANDS are attached to the 
sides of the G:isOPHAGUS, the secretion 
being conveyed to the BUCCAL CHAMBER 
by a pair of long and slender duets ; 
the LIVER is composed of dusky yellow 
follicles separated by dark grey pigment, 
and the hepatic white arterial plexus is 
very striking and distinctive. 
The REPRODUCTIVE ORGANS display 
a whitish OVOTESTIS with seattered 
lobules ; the HERMAPHRODITE DUCT is 
scarcely convoluted, and thickest in 
the middle, terminating in a_ thick, 
blunt, and  milk-white  VESICULA 
SEMINALIS; ALBUMEN GLAND some- 
what fusiform, closely lobed, whitish, 
tinged with brown ; OVISPERMATODUCT Fic. 79. 
narrow above, Ee: ample below ; the Fic. 79.—Alimentary canal of A. helvetica, 
ovipuCcY leht grey with distinct folds ; x3. (Llieniog Castle, Anglesey, Mr. T. Rogers). 
SPERM-DUCT thin and narrow above, Fic 80, Sexual oreans of Eihelaeneeaes 
thick and opaque-white below ; FREE- (Llieniog Castle, Anglesey, Mr. T. Rogers). 
OVIDUGCT of almost uniform thickness, a.g. albumen gland ; of. ovotestis ; ov. oviduct 5 
shghtly thickening below; SPERMA- pr. prostate or sperm duct; sf. spermatheca ; 
vy. retractor; wv.d. vas deferens; g. vaginal 
TIECA narrowly oval, tinged brown, gland; #.s. penis sheath, with epiphallus. 
with muscular attachment to the ovi- 
duet, its duet about double the length of the vesicle, slender above, much wider 
below, its junction with the free-oviduct concealed by the ample, whitish, and 
flocky VAGINAL GLAND; VAS DEFERENS is as usual in Huhyalinia, filiform until 
it has passed through the muscular tissue at the base of the PENIS-SHEATH, when 
there is an abrupt enlargement, which afterwards gradually diminishes until it 
joins the epiphallus near its apex, the terminal retractor being fixed to the upper 
region of the oviduct; the EPIPILALLUS is thick and oblong in shape, contracting 
to join the penis-sheath, which ¢gradually enlarges towards the base, where it again 
contracts before entering the short ATRIUM. 
The MANDIBLE or jaw is nearly a millimetre across, 
convex from front to rear, crescentic in shape, with a dis- 
tinct and somewhat acutely-pointed rostrum or beak pro- 
jecting from the middle of the lower or cutting margin. Rie) Si Mandiblelor 
The mandible generally is of a dark fawn colour, with a jaw of H. helvetica, x20. 
thickened and dark black-brown area in the centre, which (Anglesey, Mr. 'T. Rogers). 
extends quite to the apex of the beak, leaving a paler erescentic area at each side 
of the rostrum along the cutting margin. 
