Pvn H,i I'UitlS

, KELLIA. 227
The byssal sinus is about halfway up the foot on the
posterior side ; and from it the animal produces a very
delicate thread, and suspends itself freely (with the beaks
of its shell downward) by a single almost inconspicuous
fibre, which is strengthened by a double attachment at the
top. In this posture it appears to rest for some time, with
both tubes open, and the foot partly withdrawn! into the
shell. According to Mr. Clark, the byssus spun by the
kind which is found in rocks consists not merely of
delicate filaments such as free individuals of the ordi-
nary
form throwr
out when placed in a saucer, but of a
membranous plate which cannot be detached without
some force. He also says that the larger tube in free
specimens (having a thinner shell) is marked with flakewhite
longitudinal lines, which do not appear in the
rock specimens. He found in the ovary of one indi-
vidual ova in an advanced state, together with fullyformed
testaceous fry. M. Recluz has lately announced
the same fact with regard to the variety lactea. The
ova mentioned by Mr. Clark, and which through his
kindness I have had an opportunity of examining, are
bean-shaped, and closely
resemble a minute form of
Cythere. They are very different from the fry, which
are perfectly spherical. Dr. Gordon has remarked that
K. suborbicularis is occasionally seen as part of the food
of the haddock. Sometimes the shell is extremely thin,
and so transparent that the gills are distinctly visible
through it, causing the surface to appear obliquely
striated. The cartilage is always ruptured and divided
when the shell is fully opened, one half being left in
each valve. The teeth vary somewhat in shape and
relative position.
This species is the Erycina pisum of Scacchi, Bornia
inflata of Philippi, and Oronthea Montaguana of Leach,