Pvn H,i I'UitlS

CARDIUM. 293
specimens resemble punctures : colour milk-white,
with occa-
sionally a very faint prismatic hue : margins rounded on all
sides except behind, where there is a gradual slope towards
the posterior end, which in the young is indistinctly angular :
beaks very small, glossy, turning towards the anterior side ;
lunule-shaped depression rather long and deep : ligament
above the dorsal line :
short, yellowish-brown, projecting
hinge-line curved : hinge-plate narrow and sharp, occupying
between a third and a fourth of the circumference : teeth, in
the right valve one double cardinal (the plates or lobes of which
are of unequal size), with a short triangular lateral on the
anterior side and a small sunken laminar lateral on the posterior
side ; in the left valve are corresponding cardinals and
laterals, the latter on the anterior side being double : inside
polished and slightly nacreous, fluted in every part, owing to
the concavity of the outside ribs, the flutings having broad and
truncate terminations : scars slight and usually indistinct.
L. 0-4. B. 0-4.
Habitat :
Fine sand in 5-100 fathoms,
west of Scot-
land and Moray Firth, Shetland, and all the Irish coasts ;
Mr. M 'Andrew has dredged it sixty miles N.N.W. of
the Land's End in 50 fathoms. It is a local species.
According to Geikie it has been found by
Mr. Richmond
in the glacial deposits at Bute. It inhabits the seas of
Scandinavia and the western coasts of the Baltic, at
depths varying from 10 to 130 fathoms. Philippi discovered
a recent single valve at Panornii, and many in a
fossil state at Palermo and Tarenti ;
taken it alive in the Gulf of Lvons.
and M. Martin has
Clark thought that this might be a variety of C. edule.
It is, however, a much more delicate shell ; its length
is greater in proportion to its breadth, and its contour
is more oblique; the transverse scales are arched or
vaulted, instead of straight;
the interstices of the ribs
are minutely striated or punctured ; and the inside is
fluted throughout, and not towards the edge only, and
the extremities of these internal grooves are truncate or
blunt, being in C. edule sharply pointed.