140 MILAX GAGATES. 
Description.—ANIMAL comparatively slender, and usually 50 mill. or more in 
length when extended; typically of an almost uniform black above, but in this country 
more frequently of adrab, lavender or plumbeous-grey ; DORSAL-KEEL very prominent 
and sharp, especially at the caudal end, where it is abruptly angulated; it extends 
the whole length of the back, strongly indenting the hind margin of the shield 
when the animal is at rest, and is usually of the same or a darker colour than the 
body; the Bopy is longitudinally and regularly suleate, the intervening spaces being 
only slightly granulate; SHIELD or mantle ample, truncately rounded behind, finely 
wrinkled and bearing a bluntly lenticular or horse-shoe shaped unpigmented sulcus, 
which cireumseribes a somewhat protuberant and slightly darker central area 
beneath which the vestigial shell is lodged ; rooT-soLE pale, distinctly tripartite, 
the mid-area much broader than the side-areas, and separated by a deep Eee 
FRINGE same colour as side of sole, without lineoles, rather thick and rounded at 
the front, defined from the sides by a deep channel; TENTACLES moderately long and 
granulose; lower tentacles short. Mucus thick, glutinous, and colourless when in 
health, but when irritated or scalded tinged with pale yellow, and slightly milky 
from the presence of innumerable minute granules of carbonate of Jime. 
SHELL more or less elongately oval in 
shape, glistening white in colour, and some- 
what convexly rounded on the upper side ; 
APEX or nucleus subterminal and almost 
median, encircled with strong and regular 
concentric lines of growth; under-side flat, 
or even somewhat convex owing to the 
presence of an almost flat caleareous plate, 
the shell thus often presenting a double 
appearance when viewed laterally, simulating two shells placed one upon another. 
Length, 43 mill. ; breadth, 3 mill. 
INTERNALLY, the NERVOUS MATTER is Sone 
closely aggregated round the throat, the 5 
Fic. 157.—Internal shell of 7. gagates x 4. 
(Christchurch, Hants, Mr. C. Ashford). 
dark-grey and triangular cerebral ganglia 
being connected by a short broad dark-grey Fic. 158.— 
Nerve centres of 
commissure ; the buccal ganglia are whitish, Milax* gagates, 
a little more than their own diameter apart, showing otocysts 
and joined to the cerebral ganglia by dark- v) A o) (greatly enlarged). 
grey connectives ; the SUPRA-PEDAL GLAND 
is free, and only half the length of the body in 
adults, and even less in immature individuals. 
The LIVER is chestnut-coloured, the right lobe forming the posterior end of the 
visceral mass, the left is directed forwards to the KIDNEY, which has a long tongue- 
shaped prolongation beyond the right margin of the organ. 
The ALIMENTARY CANAL shows a broad and brown GSOPHAGUS; an ample 
brown CROP with white SALIVARY GLANDS adherent to its walls; the intestinal 
coils are triodromous, but owing to the strong spiral twisting to which the whole of 
the viscera have been subjected they appear much more complex; the second 
intestinal tract extends beyond the termination of the stomach, and turns in the 
eandal lobe of the liver, the rectum passing to the anal opening at the right side 
of the body without looping the retractor. 
The REPRODUCTIVE SYSTEM opens externally about half-way between the right 
ommatophore and the respiratory orifice ; the OVOTESTIS is oval and whitish, with 
large acini; the DUCT becomes ample and tortuous as it nears the albumen gland, 
where there is a well-defined VESICULA SEMINALIS; the ALBUMEN GLAND is pale 
ochreous, gelatinous and semi-transparent; the SPERM-DUCT is of an opaque milk- 
white colour and not well developed; the OVIDUCT is semi-transparent, with a tinge 
of blue; the FREE-OVIDUCT narrow and eylindrical ; the VAS DEFERENS short, 
entering the epiphallus terminally ; the PENIS-SHEATH is small 
and insignificant, with longitudinal ribbing, terminated distally 
by a large and well-marked bluish-white EPIPHALLUS, which 
is annularly ribbed internally, the ribs being visible externally 
as opaque-white specks; the basal limits are denoted exteriorly ee, 
by a distinct sphineter, and interiorly by two annular series Fic. 15).-7Sarcohe- 
P “ : 7 > A A um of Wilax gagates 
of projecting papille ; the penis-sheath enters the bulbous and — (greatly enlarged). 
bulging ATRIUM at the side within the protuberant part of 
which, opposite the penial opening, there is a smooth and ploughshare-shaped 
excitatory organ, or SARCOBELUM ; the PENIAL-RETRACTOR, which is quite slender, 
