100 LAND AND FRESH-WATER MOLLUSKS. 
* 
Genus Vitkina. 
The distinctive generic title is derived from 
the Latin word vitrum, glass. This generic 
group is a connecting link between the Slugs and 
the true Snails or Helices ; for it has the lingual 
dentition and the shield-like mantle of Limax and 
the globular external shell of Helix . They appear 
to be occasionally animal-feeders, like the slugs, 
a propensity equally possessed by some of the 
Helices. Vitrina may be readily distinguished 
from Helicella , by the absence of an umbilicus ; 
for all the shells of species of the latter are per¬ 
forated. The genus is represented in Britain by 
only one species :— 
Vitrina pellucida— (the Green Glassy Snail) 
(PI. VI., fig. 43).—The body of this snail is elon¬ 
gated, too large to allow of the animal retracting 
completely into the shell. The mantle is pro¬ 
duced into a shield and reflected over the front 
of the shell when the animal crawls, and furnished 
with a tongue-like lobe on the right side; the 
lingual teeth are like those of Limax , of 100 rows 
of 75 each, and the jaw resembles that of the 
true slugs and cellar snails, in being strongly 
arched from before backwards, produced into a 
beak, smooth or nearly so. 
The beautiful greenish-glassy shell of this 
