Pvn H,i I'UitlS

78 PECTINID^E.
its own. This remarkable construction is funnel-shaped
with the larger end contracted, and sufficiently wide to
admit of the Lima moving freely up and down, but not
turning round in it. Here it lives, secure from prowl-
ing
fish and crabs. The case is lined inside with a
closely-woven net of byssal threads, plastered
over with
slime or excrement. This smooth and soft lining con-
tains a quantity of Diatom- cells, and yields a rich
harvest to those who collect these exquisite organisms
for microscopical examination. Such remains of per-
petual
feasts remind one of the similar exuviae which are
found at the bottom of a spider's web. No species of
Lima is noticed in Dr. Gould's '
Invertebrata of Massa-
chusetts/ or in any other work on the conchology of
nor has Dr. Philip Carpenter, in his
the United States ;
elaborate list of the Mollusca inhabiting the north-west
coast of America, enumerated any as belonging to the
northern fauna of that extensive district.
The very ancient genus Plagiostomus of Lhwyd (Pla-
giostoma of Sowerby's '
Mineral Conchology ') is con-
sidered by some palaeontologists to be identical with the
present genus. It may be connected with it through
the genus Limea of Bronn, and form a passage to Spondylus.
Poli used the name Glaucus for the animal of
the present genus.
A. Shell equilateral, with a straight outline.
1. Lima Sar'sii*, Loven.
Limea Sarsii, Lov. Ind. Moll. Scand. p. 32.
Body milk-white : mantle set with large, thick, and ringed,
but not numerous cirri or tentacles.
Shell roundish -oval, slightly oblique, convex, rather solid
* Named in honour of Professor Sars, an eminent Norwegian zoologist.