WINKLES. 199 
GENUS LITTORINA. 
The shell in this common and well-known genus 
is spiral with but few whorls, generally more or 
less oval in form, and thick and solid in substance. 
The spire is sometimes pointed, as in the common 
Periwinkle (Z. littorea) ; sometimes obtuse or round, 
as in the equally common Yellow Winkle (L. ner?- 
toides). ‘The aperture is round and entire; the 
outer lip is sharp-edged, thickened within. The 
operculum is horny and elastic; its spire consists 
of a few turns, rapidly enlarging, with a central 
nucleus. 
In most of our seaport towns, and in many of 
our inland cities, the Periwinkle is sufficiently 
familiar, from its being so commonly sold by mea- 
sure as human food. ‘The animals are found by 
thousands on rocks at low-water, or on the mud 
left exposed by the receding tide in harbours and 
estuaries; they are collected by the children of 
fishermen, boiled, and hawked about the streets at 
alow price. They are eaten not infrequently by 
persons above the lowest grade of society, not 
from necessity, but from choice; though to most 
uneducated palates they are coarse, tough, and 
indigestible. 
The Periwinkles are able to bear long-continued 
exposure to the air with impunity. The species 
just mentioned may be observed adhering to the 
rocks by hundreds under a hot sun, and that for 
hours together; but a smaller kind (ZL. rudis),— 
which may be recognised by its being frequently 
found white, pale-green, yellow, and orange in 
eolour,—habitually resides in hollows of rocks that 
are elevated many feet above the range of high- 
