Pvn H,i I'UitlS

CYAMIUM. 259
tracing of them. You will see that in two of the figures
the tube is exserted : but the animal is rather shy in
extending it, and it can only be seen by watching the
opportunity. It is probably the anal siphon, as is supposed
to be the case in Lucina [Loripes], — the branchial
siphon being either very short or only formed by a fold
in the open mantle, as in some other genera." I have
myself failed to detect any slender tube such as Mr.
Alder has described, although during the last two years
I have examined a great number of living and active
individuals on the spot and under extremely favourable
circumstances. Subjoined is the result of my observa-
tions, which were noted at the time of their being made,
with respect to the shape and position of the tube and
foot. The excretal or anal tube is small, button- shaped,
and almost sessile. It is situate on the upper part of
the posterior or broader side of the shell. This process
is formed out of a fold or contraction of the mantle, and
slightly separated by a raised edge from the long ventral
opening. It is occasionally protruded, but never to a
greater extent than the one-hundredth part
of an inch.
When this takes place the lower side is higher than the
upper, and appears, when viewed sideways,
like an ex-
ceedingly minute tooth or conical point. Being nearly
transparent, the raised edges cannot be seen, unless the
The mouth
object is placed in relief on a black ground.
or orifice of the tube is roundish-oval and plain. I
from it. No
repeatedly observed excretal pellets ejected
other tube or orifice was perceptible on the same side.
The ventral gape, occupying the middle of the open
and wide. It serves for the ad-
valves, is very large
mission of food, as well as of water to aerate the gills.
There was always a current passing into it, charged
with animalcula. The edges of the mantle towards the