Pvn H,i I'UitlS

LASJEA. 217
Genus III. LAS^E'A*, Leach. PL V. f. 2.
Body oval : mantle folded on the anterior side (being the
longer and larger end of the shell), so as to form a wide, but
short and
incomplete, incurrent tube : the excurrent tube is very
inconspicuous, placed on the opposite side : foot long, tongue-
shaped, protruding when in motion through
current tube at its base.
Shell roundish-oval : beaks straight :
a slit in the ex-
cartilage long and
cylindrical, divided or split lengthwise, and clasping the
hinge-plate, in each valve, on the smaller and narrower side
of the shell, being the posterior end : hinge containing in the
left valve a minute thorn-like cardinal tooth, and in each
valve two remarkably strong lateral teeth.
The late Captain Brown proposed this genus in 1827,
on the authority of Dr. Leach, for the Cardium rubrum
and although he says nothing about the
of Montagu ;
animal, and not much more about the shell, I think the
genus is a good one, and I therefore adopt the name
above given to it. M. Recluz, apparently unaware of
his having been anticipated, gave in 1843 another name
(Poronia) to the same genus; but his description is
positively incorrect. He says of the animal, that it has
on the posterior side two lobes, and two tubes which are
disunited ;
and of the shell, that the hinge has two cardi-
nal teeth in each valve, besides lateral teeth, and that
the cartilage is placed in an oblique groove. It will be
seen that my description of the generic
characters is
very different from that of M. Recluz : and were it not
for the certainty that we both mean not only the same
genus, but also the same species, I could not believe
that our respective descriptions had been drawn from
the same object. The present genus is intermediate
between Montacuta and Kellia, and partakes of the
* A meaningless name ;
little shield.
possibly a corrupt derivation from Xaiai)iov, s