20 
LITTORINID^. 
stone districts; England and Wales (^Lister), ^ Scot- 
land, Edinburgh. 
Animal grey-brown. 
Shell half an inch long, and four-tenths of an Inch 
wide, solid, grey or purplish-yellow, mostly purple 
at the tip, often marked with two rows of purplish 
brown spots ; spire composed of five rounded volu- 
tions, marked with numerous close-set raised spiral 
striaB and finer longitudinal ones between them; 
aperture round with a smalt angle at top, and an um- 
bilicus behind the pillar ; operculum hard, horny ex- 
ternally, and marked with a single depressed spiral 
line, from which some very fine strise radiate towards 
the circumference. 
Lister {Tab. Anat. iv. f. 1. 2. 3.) gives some ac- 
count of the anatomy ; and a very detailed description 
has lately been published by the Rev. Mr. Berkeley 
{Zool. Journ. iv. 278.). 
The tips of the tentacles have a bright brown 
spot very visible to the naked eye, which Montague 
considered as a second eye. It is the organ of 
smell. The tentacles, in repose, are annulated, 
resting on the sides of the trunk. 
Brard describes two unequally compressed carti- 
laginous pieces, one on each side of the buccal cavity. 
They are rounded on one side, thin and sinuous on 
the other ; slightly tubercular and whitish. 
Earn. 2. LITTORINID^. 
Trunk produced and wrinkled, not retractile ; ten- 
tacles far apart^ on the side of the head ; eyes 
