XXVI1 MOLLUSCA OF SOMERSET. 
Helix aspersa, Miiller (dominant), associated with 
Helicella virgata, da Costa. 
Helicella caperata, Montagu. 
Helix nemoralis, Linné. 
Hl. aspersa is usually very abundant, such broad-leaved 
plants as Rumex crispus, Linné, and Cynoglossum officinale, 
Linné, affording a welcome retreat during periods of drought. 
The homing instinct of this species may be well seen on a hot 
morning following a wet night, when many isolated plants are 
surrounded at distances varying from a foot to a yard by 
belated individuals who failed to gain the shade and protective 
screen reached by their more punctual brethren. 
Behind the Sea-couch Grass association we have the high 
dunes capped with Marram Grass (Ammophila arenaria, Link). 
(Plate 1, fig. 2). The side of the dune which faces the sea is 
always steep, but the slope never exceeds 30°, and the sand is 
continually blowing over it to the lesser slope on the leeward 
or landward side. 
On very windy days countless dead shells of Paludestrina 
stagnalis, Baster ; Helicella barbara, Linné; Helicella virgata, 
da Costa, and Jaminia muscorum, Linné, are often blown into 
little heaps up the dune face, rolling back again between 
the gusts. Helicella itala, Linné, and H. caperata, Montagu, 
also occur with them but in lesser numbers. At the base of 
the dunes bleached shells of Helix aspersa, Miller, lie in 
hundreds. 
Amongst the Marram Grass and on the leeward slope of 
the dunes we find the following association : 
Helicella barbara, Linné (Helix acuta, Miilier), dominant. 
Jaminia muscorum, Linné (=Pupa marginata, Draparnaud), 
sub-dominant. 
Helicella virgata, da Costa. 
Helicella itala, Zinné (=H. ericetorum, Miiller). 
Helicella caperata, Montagu. 
Helix aspersa, Miller. 
