Pvn H,i I'UitlS

GALEOMMA. 191
into delicate fibrous filaments that instantly adhered to
the saucer : we
detached the animal several times ; the
byssus was always left, and a new one formed. On
we found
leaving it for the night, in a marked position,
in the morning that it had detached itself by abandon-
ing the byssus, and had formed another at a considerable
distance. The animal marches with great rapidity,
by flatting the valves into the form of a circular disk ;
it then, by the foot, aided by the muscular margins of
the mantle, makes rapid progression. It marched across
the saucer before ten could scarcely be counted." Mr.
Alder noticed a peculiar expansion of the mantle, which
invests the shell like a membrane. Philippi had previously
remarked that this membrane resembles the
true skin of vertebrate animals ; but Alder has given a
farther explanation of its structure. He says " it is a
continuation of the true skin, and consists of two layers ;
the lower of which is slightly muscular, and under the
microscope the muscles may be seen interlacing each
other in all directions. The outer layer is granular, and
is covered with tubercles, which possibly, when the ani-
mal is alive, may rise into papillse. The want of an
epidermis appears to be thus supplied." The interesting
particulars above given of its organization make us
anxious to know more about this wonderful mollusk ;
and it is to be hoped that the investigation will be con-
tinued by Mr. Alder, or prosecuted by some other ob-
servant naturalist. The animal is hardy, and could be
safely sent by post, packed in Chondrus crispus or some
stiff sea-weed, to any place within reach of the sea. The
number, position, and nature of the siphonal tubes have
not yet been satisfactorily made out. Philippi describes
one only, Mittre two (besides an anomalous organ re-
sembling the large tentacle of Lepton squamosum), while