a 
VITRINA PELLUCIDA. 
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The MANDIBLE or jaw is nearly a mill. fronmside to side, strongly convex from 
front to back, and of a crescentic shape, of a delicate amber colour, and bearing on 
its lower or cutting margin a prominent but bluntly-rounded median projection or 
beak ; ends somewhat square and placed at an obtuse angle to the lower margin ; 
the whole anterior surface is delicately cross-striate, while the line of attachment 
Fic. 3. Fic. 6. BGs as 
Mandible or jaw of Vitvina pellucida, showing some of the stages of its development to maturity. 
Fic. 5.—Jaw of a young individual, magnified (after Wiegmann). 
Fic. 6.—Jaw ofa half-grown specimen, magnified (after Wiegmann). 
lic. 7.—Jaw of an adult, collected at Grantchester by Mr. Hugh Watson, and prepared by the Rev. 
Prof. Gwatkin, x 30. 
of the elasma is indicated by a darker sub-central line parallel with the lower 
margin, while a second darker line is seen near to and parallel with the upper convex 
margin indicating the depth of its insertion in the tissues. 
The LINGUAL RIBBON is about one-and-half mill. in length, and of the usual 
oblong shape, composed of about one hundred transverse rows of teeth, each row 
containing a tricuspid central tooth, flanked by nine perfect laterals, arranged e 
chevron, and which are really only bifid, the endocone being obsolete and withont 
cutting point; some observers have, however, described a supplementary endoconic 
cutting point as existing on the mesocone of the admedian teeth ; the transition to 
the aculeate marginal teeth is abrupt, and the change in the direction of the rows 
very perceptible; the marginals are usually about twenty-four in number, and are 
all ‘distinctly and strongly bifid, with a subsidiary serrate continuation along the 
outer margin of the reflected portion of each tooth, due to the presence of three or 
more sharply defined but minute denticulations. 
Fic. 8 & 9.—Diagram showing the direction of the transverse rows of denticles and a row of representative 
teeth from the lingual ribbon of Vztvina pellucida X 160. The specimen collected at Grantchester by 
Mr. Hugh Watson, and the palate prepared by the Rev. Prof. Gwatkin. 
The formula of a Grantchester specimen, collected by Mr. Hugh Watson, and 
prepared by the Rey. Prof. Gwatkin, is 
224+ 34343427 x 100 = 7,300. 
Reproduction and Development.—The congress of this species 
does not appear to have been observed, but the egg-clusters, each com- 
posed of from eight to fifteen eggs, adherent together by albuminous 
matter, have been found from September to February. 
The great Swedish naturalist, Nilsson, collected some individuals at the 
end of January, which he kept in captivity, and on February 19th noticed 
some eggs amongst the decaying leaves. ‘hese were roundly-oval, white, 
and subpellucid, with a central opaque spot, and were placed in little 
clusters of eight or nine eggs each. In the beginning of March, signs of a 
slow rotatory movement of the embryo were noticed, and on the 21st and 
22nd of March the animals were excluded, 
he young do not increase much in size during the summer mouths, but 
keep quite small, and are therefore difheult to find. They attain full 
growth during the colder months of the year, and die off in the early 
spring after a life-period of twelve to fifteen months. 
