222 LAND AND FEE SB-WATER MOLLUSKS. 
that of a brilliant white organ lodged among the 
convolutions of the intestine; it contains a mul¬ 
titude of solid concretions, composed of an 
organized skeleton and incrusting salts.” {Cla- 
parede.) 
This species is abundant in the localities where 
it is found, but is alwavs confined to calcareous 
* «/ 
soils, especially those of the oolites and chalk. 
It dwells in hedge-rows and on the margins of 
woods, or more rarely on open downs and hills. 
It ranges as far north as Yorkshire, is absent in 
Ireland and in Scotland, and is distributed over 
Central and Southern Europe, and extends to the 
Canaries and Algeria. 
The restriction of this species to limestone soils 
is very marked. It occurs throughout the whole 
of the chalk and oolitic ranges in great abundance, 
more sparingly on the Mountain Limestone hills. 
Dr. S. P. Woodward informs me, that in Norfolk 
it is found in great profusion on the bosses of 
chalk that appear among the overlaying Ter¬ 
tiary gravels and clays, and is not met with 
in the intervening areas. Notably also, the 
junction of the chalk with the low alluvial plains 
in the Wealden district is very accurately indi¬ 
cated by this shell. Thus, although the hilly 
districts of the Hastings Sands apparently seem 
favourable to the existence of this snail, it does 
not occur there, nor upon the plains of alluvium 
