Pvn H,i I'UitlS

position not being homogeneous,
MONTACUTA. 205
the base becomes
hardened to such an extent, that a cup -shaped process
or "ossicle" is formed, which can be separated from
the shell. It can only be detected in fresh specimens
before the cartilage has dried up; and the latter is
seldom preserved, owing to its elastic nature and slight
attachment to the pit, which is fixed and forms part of
the shell. The genus Thracia has nearly the same kind
of process.
Gould was of opinion that the present genus and
Kellia ought to be united, or else that the one might
merge in Ungulina of Daudin, and the other in Erycina
of Lamarck. Nyst referred Montacuta to the lastmentioned
genus. But although Lamarck states that
the ligament in Erycina is internal, the hinge is de-
scribed as having cardinal as well as lateral teeth. The
structure of the hinge in Ungulina is very different from
that in Kellia.
Several species are noticed by Dr. Philip Carpenter
as inhabiting the Gulf of California.
1. Montacuta substria'ta *J Montagu.
Ligula mbstriata, Mont. Test. Brit. Suppl. p. 25. M. sv.bstriata, F. & H.
ii. p. 77, pi. xviii. f. 8, 8 a, and (animal) pi. O. f. 2.
Body whitish and nearly transparent: mantle having its
margin simple, and largely open in front for the passage
foot :
of the
gills large and conspicuous : foot muscular, transparent,
very much longer than the shell, issuing from the broader end,
tapering to a disk-like point, and furnished at the heel with a
byssal groove.
Shell varying in shape from a long to a short oval, with an
oblique outline, rather convex, not very thin, semitransparent,
usually of a dull aspect, but sometimes glossy :
about a dozen very slight
sculpture,
and indistinct ribs, which radiate
from the beak but do not quite extend to the front margin ;
there are also a few white longitudinal streaks, and concentric
* Slightly striated.