200 PECTINIBRANCHIATA.—TURBINIDA. 
water. But their gills are constantly moistened 
by a minute quantity of sea-water contained in the 
cavity of the body; and this is prevented from 
evaporation, partly by the close adhesion of the 
margin of the shell to the rock, and partly by the 
tightly-fitting operculum. 
Indeed there is reason to believe that this and 
some other species of the genus spend the winter 
in the air, hybernating, like the Snails. ‘“ Mr. 
Gray found that many individuals of L. petrwa, and 
some of LZ. rudis, were in this condition, during his 
stay at Dawlish. They were attached to the rocks 
several feet above the reach of the highest autumnal 
tides ; the foot was entirely retracted ; and a mem- 
branous film was spread between the rock and the 
edges of the outer lip of the shell; the gills were 
only moist, the branchial sac being destitute of 
that considerable quantity of water which exists in 
it in those of the same species which are adherent 
to it by their expanded foot. In this torpid con- 
dition the individuals observed by Mr. Gray con- 
tinued during the whole of his stay, which lasted 
for more than a week. On removing several of 
them, and placing them in sea-water, they recovered 
in a few minutes their full activity.”’* 
In Sweden the common people affect to prognos- 
ticate the weather by the position of the Periwin- 
kles ; when these ascend the rocks, it is considered 
as a sure sign that a storm is near, as their instinct 
leads them to place themselves out of the reach of 
the dashing of the waves; on the contrary, when 
they descend upon the sands it is supposed to indi- 
cate calm weather. I much doubt, however, the 
fact of any such connexion between the habits of 
* Proc. Zool. Soe. iii. 116. 
