GENUS VITRINA. * 
INTERNALLY, the MANDIBLE or Jaw is oxygnathous, closely resembling 
that of the Limacide ; the dentition also displays the same affinity by the 
presence of the numerous aculeate marginals; the REPRODUCTIVE ORGANS in 
some species show the glandular pad upon the FREE-ovIDUCT, which is so 
characteristic a feature of the //yaliniw, while the suPpRA-PEDAL GLAND is 
well developed and compact and occupies about one-third the length 
of the foot. = 
The species of this genus in external characters are intermediate between 
the slug and the snail, having the external spirally-coiled shell of the latter 
and the dorsal shield of the former group; they are also closely allied inter 
se and difficult to separate into the various recognized species without the 
aid of their internal organization, which shows far greater differentiation 
than the outside form; thus the V/trina elongata possesses a hollow 
chitinous dart which acts also as the excretory duct of an internal gland, 
and while, therefore, probably analogous to the Helicine dart, is not its 
homologue, though Simroth is inclined to think otherwise. Vitrina brevis 
is furmshed with a fleshy papilla or sarcobelum, which has also a 
glandular connection, while many of the tropical Zonitida show attinity 
in this direction by possessing similar glands and perforate chitinous 
darts, which are sometimes impregnated with lime. 
Food and Habits.—The Vitrinw are truly omnivorous, and even 
predaceous, bold, active, and very hardy, and apparently quite indifferent 
to cold, as they have been frequently observed crawling over the snow even 
during keen frost; they frequent by preference moist and shady places, and 
are nocturnal or crepuscular in habit, usually coming forth at dusk from 
their hiding places, to which they again resort before daybreak. he late 
Hugh Cuming has recorded that mollusks referred by him to Vitrina, but 
really belonging to Helicarion, were very abundant in the Philippines, 
and that he was particularly struck with their activity, as they were able 
to leap from the ground by the sudden muscular action of the foot. Mr. 
Benson confirms this peculiar habit as existing in allied forms, as he has 
observed an East Indian species spring several inches from the ground ; 
while a recent observer ascribes to our native Vitrénw similar but even 
more remarkable habits. 
Geographical Distribution.—The genus as now usually restricted 
is a group of small and delicately-shelled species, found chiefly in the cold 
and temperate regions of the northern hemisphere, being said by ‘Tryon 
to be replaced by Helicurion and other groups in the countries beyond 
the limits of its range. 
The truth of our location of the area of greatest evolutionary activity in 
Mid-Europe is again further emphasized and confirmed by the present 
group, in which evolutionary progress les m the direction of the atrophy 
and eventual loss of the shell, a feature most advanced in the endemic 
Vitrine of that region. 
Geological History.— A species of Vitrina, named rillyensis by 
Boissy, has been reported from the Lower Hocene of Irance, and a Vétrina, 
named oblique by Meek and Hayden, is found fossilized in North 
America ; while Prof. Sandberger indicates the genus as occurring 11 
Germany in the deposits of the Lower Kocene, Lower, Middle, and Upper 
Miocene, and Middle and Upper Pleistocene, 
