HYALINIA CRYSTALLINA. 109 
Description.—The ANIMAL is of a semi-translucent greyish-white, slighter 
darker above; MANTLE thin, translucent with minute milk-white specks ; rooT 
whitish, narrow and acutely pointed behind; OMMATOPHORES moderately long, 
black or blackish, due to the eye retractors which also show as a pair of parallel 
dark lines through the skin of the back; KYEs jet black and very distinct. 
SHELL slightly convex above and more convex beneath, and without basal 
opacity ; thin, brilliantly glossy, transparent, greenish-white, or quite crystalline, 
and oceasionally somewhat opalescent, becoming quite opaque after the death of 
the animal; very finely and minutely striate in the line of growth, and slightly 
Fic. 147.—Hyalinia crystallina Miill , showing frontal, basal and upper aspects, x 6 (after Clessin). 
puckered at the sutures; EPIDERMIS very thin; WHORLS 44-5, very slowly and 
regularly increasing in size; SPIRE slightly raised; suTURE distinct ; MOUTH 
semilunar, sometimes with a slight internal thickening or rib; the under surface 
Without any opacity, and the UMBILICUS narrow and almost punetiform. 
Diam., 34 mill. ; alt., 1 mill. 
When containing the living and retracted animal, the shell appears of a trans- 
Incent white, becoming pale yellowish-brown on the inner whorls; the black 
eye-specks are visible through the shell-wall, 
they lie beneath the periphery of the shell, 
half-a-whorl from the aperture and about two 
millimetres apart. 
The JAW or mandible is slightly arched or y x 
flatly crescentic, of a very pale amber or almost (Aa) 
colourless and translucent, the ends are rounded a tess) : P 
. 1 r Vr “ 1G. o.— Wandibie or Jaw Oo 
and there is a very broad and blunt median jp) Ue iy Ps Bae Cee 
projection or beak in the middle of the concave Yorks., Mr. F. Booth) from a prepara- 
margin ; the elasma is delicate and colourless. tion by Rev. Prof. Gwatkin. 
The LINGUAT. RIBBON is described by Dr. Lehmann as somewhat linear in shape, 
and bearing about eighty transverse rows of about thirty teeth each. The median 
tooth is simply conical, with a strong mesocone and a smaller ectocone at each 
side, borne upon a quadrate base, and is smaller than the adjacent teeth. The 
laterals are also borne on a quadrate base, and possess a conical mesocone, and are 
described and figured as with an endocone and ectocone. The marginals are 
elongate, but strictly aculeate, and supported on an acutely triangular base. 
Herr Clessin describes the dentition as consisting of a median tricuspid tooth, 
three lateral teeth with two to three cutting points and eighteen aculeate mar- 
ginals, and Heer Schepmann similarly describes the lingual armature of Hyalinia 
subterranea ; the laterals in this species are, however, not really tricuspidate as 
described, the endocone being apparently constituted by the inner angle of the 
basal plate. A specimen from Shipley Glen, Yorkshire, showed a trifid mid-tooth, 
three bicuspidate laterals, and sixteen marginal teeth. 
sin nin (2 ft A» 
Fic. 149.—Representative denticles from a transverse row of the teeth of Wyadinia crystallina var. 
subterranea, from Rhoon, near Rotterdam x 600 (after Schepmann). 
The ALIMENTARY SYSTEM of the var. subterranea is described by Dr. Lehmann 
as showing a whitish OVOTESTIS with direct SALIVARY DUCTS, 23 mill. in length ; 
the Crop is somewhat curved and delicately spotted with white, the cardiae enc 
narrows abruptly, and shows a small ccecum, while the pylorie end is somewhat 
sac-like ; the INTESTINAL TRACT makes two turns within the digestive gland; the 
DIGESTIVE GLAND or liver is finely granular in substance, of a pale brownish or 
yellowish-grey with white fleckings ; the RENAL ORGAN or kidney is large and 
somewhat triangular, with thickened ends, of a granular consistency, and of a 
greyish-white colour, 
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