Pvn H,i I'UitlS

LASyEA. 219
the littoral zone, where they congregate in vast num-
bers, at the roots of small seaweeds, as well as in the
crevices of rocks and in the empty shells of Balani. On
some coasts they live as much out of the sea as in it,
a sufficient supply of water being retained within the
close-fitting valves to keep the gills
moist until the
return of the tide ; and in many cases they must fast for
a long time, because they are found in places which are
covered by the sea at high springs only.
A little fresh-
water bivalve (Pisidium pusillum) is also occasionally
amphibious. We have but one species of Lascea, and
that is viviparous. Other species, however, have been
noticed in various parts of the world :
"
Prythee, think
There's livers out of Britain."
1. Las^ia rtj'bra*, Montagu.
Cardium rubrum, Mont. Test. Brit. p. 83, tab. 27. f. 4.
F. & H. ii. p. 94, pi.
Kellia rubra,
xxxvi. f. 5-7 (as Poronia rubra), and (animal)
O. f. 3.
pi.
Body white : mantle having its margin apparently plain and
without tentacles : excurrent tube sessile and concealed within
the mantle : foot broad at the base, the extremity being rather
rounded than pointed ; its bluish-white and transparent hue
is variegated by a line of dull but intense flake-white, which
runs from one end to the other.
Shell oval, with often a circular or triangular and rather
oblique outline, ventricose, not very thin or glossy : sculpture,
distant lines of growth and close-set wavy concentric striae,
besides more numerous but much finer longitudinal striae,
which are so excessively minute as only to be seen with a
powerful lens : colour milk-white, tinged more or less deeply
with purplish-red, especially towards the hinge : epidermis
yellowish, rather thick : margins somewhat truncate and
rounded at the smaller or posterior end, slightly curved in
front, with sometimes a byssal sinus or indentation in the
* Eed.