Pvn H,i I'UitlS

426 MACTRID^E.
curved on the anterior side and nearly straight on the other
side : beaks sharp, triangular, and incurred, turned towards
the anterior side umbones ; swollen, prominent and projecting
: ligament short and comparatively slight, reddish -brown :
cartilage large, but not otherwise different from that of its
congeners : hinge-line curved : hinge-plate extremely broad,
reflected over the dorsal margins, strong, not flexuous because
the cartilage-pit is scarcely advanced beyond the inner edge of
the plate : teeth, in the right valve two short erect cardinals,
united behind and diverging from each other at a right angle ;
laterals two on each side, and of the same description as in
M. stultorum ; in the left valve two united cardinals, and a
single lateral on each side— similar to those in the last species,
except as to size and in the laterals rising from the beak to a
rounded point at each end and then abruptly falling and continued
towards the front in a ridge-like form : inside coloured
like the outside and showing the rays, slightly and irregularly
scar as in the last
striated in a longitudinal direction : pallia!
species : muscular scars B. 4.
triangularly oval, well marked. L. 3.
Var. luteola. Shell creamcolour, without rays but stained
with reddish-brown or chestnut on the dorsal margins.
Habitat :
Confined
to a very few parts of our south-
ern shores, viz. Hayle, Cornwall, where single valves
were first found by Miss Pocock, subsequently by
Lieut. -General Bingham, and since by Mr. Templer,
Herni and Guernsey, at
Mr. Jordan, and Mr. Hockin ;
unusually low tides (Lukis) . The
variety is from Hayle.
Fossil in the Red Crag (S.Wood); Tarenti (Philippi).
The foreign localities are the north of France; Spain
and Portugal (Chemnitz) ; Gulf of Lyons (Martin) ; and
the Mediterranean, including Algiers (Poupillet).
A series of this handsome shell was presented to me
by the late Dr. Lukis, who afterwards sent me an ex-
quisite drawing of the animal, which has enabled me to
give a description of that part. He observed that " when
the tide recedes it buries itself two or three inches in
the sand ; and when the tide rises it bestirs itself like