128 LAND AND ERESH-WATER MOLLUSKS. 
and Cyclostoma elegans. Now the strata embraced 
within that line of coast are composed of sand¬ 
stones^ sands, and clays belonging to the Green¬ 
sand and Wealden formations, and the recent 
alluvial deposits. 
Though much has been written for and against 
the restriction of snails to certain soils, never¬ 
theless I adduce the above case as a very 
striking example in favour of the association of 
certain land shells to particular kinds of rocks, 
though not necessarily to any given formation. 
The specific name is usually written Carthu- 
siana , but Mr. J. G. Jeffreys thinks “ the original 
spelling of Cartusiana ought to be retained.” 
Helix rueescens — (the Rufous Snail) (PI. VIII., 
fig. 76).—So called from the rufous-brown of the 
shell. Though usually of this colour, yet it pre¬ 
sents intermediate shades, even to a pure white. 
The shell is depressed, slightly angular below, 
composed of six or seven whorls; the aperture is 
oblique, semielliptical, thin, and slightly reflected, 
with a broad internal band, distinctly visible 
from the outside; the umbilicus is narrow, but 
distinct. In very young shells the exterior is 
clothed with hairs, and in this state may be con¬ 
founded with H. hispida , but is easily distin¬ 
guished by the keel on the margin of the outer 
whorl, whilst in IT. hispida the last whorl 
is rounded. 
