Pvn H,i I'UitlS

204 KELLIID^E.
Genus II. MONTACU'TA * Turton. PL V. f. 1.
Body oval, rather thick : mantle protruded, and fringed with
short cirri : eoccurrent tube sessile : foot large, tongue -shaped.
Shell triangularly oval or oblong : cartilage proportionally
large, placed
underneath the beak on the smaller and narrower
or posterior side : hinge furnished with two strong
in each valve.
Montagu preeminently
lateral teeth
deserves to have his name
commemorated in the present genus, because all the
known British species were discovered and admirably
described by him. Two out of the three are dwellers
in mud : the other has a singular habitat, being inva-
riably found attached to the spines on the under side
of Spatangus purpureus and other Echinoderms of the
same kind.
The founder of this genus, Turton, says
hinge
that the
is furnished with cardinal teeth but with no lateral
ones. This appears to be a mistake ; at least I con-
sider the scheme of dentition to be exactly the reverse
of the above. The entire space under the beak in the
hinge of each valve is occupied by the cartilage ; and
this is the only place where cardinal teeth must be
looked for. The teeth in all the British species of Mon-
tacuta are long and laminar, one on each side of the
cardinal area, and diverging obliquely inwards. A deep
cavity or indentation is thus formed in the hinge, resem-
bling the letter V reversed, and enclosing the cartilage.
The sides of this letter represent the usual shape and
position of lateral teeth. Cardinal or hinge
teeth lie
immediately under the beak, and are either tubercular
or short. The cartilage is in some species calcined at
its point of attachment, and in consequence of its com-
* Dedicated to the memory of Colonel Montagu,
logists.
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