Pvn H,i I'UitlS

orifices :
of the body :
ISOCARDIA. 299
gills free, concealed between the mantle and the rest
foot very muscular, orangecolour.
Shell almost spherical, solid when adult, of a dull hue :
sculpture, faint concentric striae, with occasional deeper lines
of growth : colour yellowish-white, variegated in the young by
zigzag streaks of reddish-brown : epidermis chestnutcolour,
rather thick, covered with extremely numerous rows of very
short fine bristles, which are of a darker colour, and radiate
from the beak to the margins, except on the upper part of the
anterior side where the cilia are wanting : man/ins curved in
front, sloping upwards on the anterior side to a blunt angle
formed by its junction with the dorsal margin, obliquely
truncate at the posterior side, which is indistinctly sinuous ;
dorsal margin projecting : beaks excentric, gracefully recurved
and making an incomplete whorl : lunule forming a broad ex-
cavation below the beaks, and enlarging rapidly during the
progress of growth : ligament strong and raised, dark reddish -
brown, following the bend of the posterior dorsal margin :
hinge-line curved: hinge-plate thick and broad, reflected outwards,
occupying rather more than one-third of the circum-
ference : teeth, in the right valve two cardinals, the outer of
which is laminar and nearly parallel to the hinge-line, and the
inner is shorter, very much thicker, and cloven obliquely;
between the latter tooth and the iuside of the shell is a deep
socket for the reception of a similar tooth in the opposite
valve ; lateral tooth short and triangular ; the left valve has
two cardinals corresponding with those in the other valve,
except that the outer one is cloven obliquely, and the socket
the lateral tooth
is placed on the inside of the thicker tooth ;
in this valve is longer than that in the right valve, but not so
high: inside chalky, with sometimes a faint tinge of fleshcolour,
irregularly furrowed lengthwise, apparently in con-
sequence of an unequal secretion by the mantle : pallial scar
broad and shining : muscular scars rather large, that on the
anterior side being remarkably deep. L. 4. B. 3-8.
Habitat : Muddy
ground
in 4-40 fathoms on the
coasts of Devon and Cornwall, east and south of Ireland,
and west of Scotland. Laskey
is said to have taken it
off St. Abb's Head. It is not generally distributed,,
although tolerably plentiful in certain places. Searles
Wood has recorded it as a fossil of the Red and Coral-