WATER SNAILS. PA a 
length of which: is about one-third the diameter 
of the shell. The animal, when walking in the 
water, carries the shell inclined at an angle of 
from 70° to 80°. 
The shell is finely striated longitudinally ; the 
epidermis is raised into deciduous bristles on the 
striations, also minutely striated transversely ; 
convex above and below, thin, pellucid, and 
whitish; about one-fourth of an inch in diameter ; 
the whorls five, the last one disproportionately 
enlarged. 
It is a common species. 
PLANORBIS GLABER—(the Smooth Coil Shell) (Pl. 
XI., fig. 126).—The nearest ally to this species 
is P. albus, from which it differs in its smaller 
shell, which is smooth; in the more rounded 
whorls, the upper side being more convex ; and, 
lastly, in being destitute of the strong spiral 
strie. 
P. glaber was first described by Mr. Jeffreys, 
who states that he only knows about twenty 
localities for it m England and Scotland; it is 
rather a northern than a southern form; it has 
been found in the neigbourhood of Belfast, Ire- 
land, and in three other localities in the north- 
east of the island. It is distributed throughout 
the greater part of the continent, and ranges 
from Sweden to Corsica and Algeria. 
PLANORBIS NAUTILEUS—(the Nautilus Corl Shell) 
