154 LAND AND FRESH-WATER MOLLUSKS. 
Shell) (Pl. IX., fig. 97)—is one of the most 
common of the land mollusca throughout the 
British isles. It frequents old ivied walls, about 
rocks, under stones, among moss and herbage 
and dead leaves; from the sea-shore to great 
elevations. 
The shell is oblong, cylindrical, glossy, yel- 
lowish-brown or dark horn-colour, composed of 
six rounded whorls, which are faintly and irre- 
gularly striated in the line of growth; the 
aperture is subangular ; the lip is thickened and 
much reflected, and white or pale yellowish-grey 
on the inside; a single tooth occupies the angle 
formed by the junction of the outer lip; there 
is a small and narrow umbilicus; the length of 
the shell is two-twelfths of an inch, and the 
breadth about half. It is subject to variation in 
form and colour: some want the tooth; speci- 
mens with two teeth have occurred to collectors ; 
others have the shell whitish or colourless. 
This species is Ovoviviparous. 
Pura muscorum—(the Margined Chrysalis Shell) 
(Pl. IX., fig. 98)—is very closely allied to P. 
umbilicata, but differs from it m being more 
cylindrical, with the last whorl smaller; the 
mouth. is more oval, less triangular, and the 
tooth is placed centrally and considerably within 
the aperture, but is, however, often absent. It 
is more especially to be distinguished by the 
