Pvn H,i I'UitlS

356 VENERIDiE.
brown ; the upper pair do not cover the lower, and they are
decussated on both surfaces by the network of the circulatory
vessels : palps small, triangular, striated on the inner, and
smooth on the outer surface :
foot muscular, slightly bent or
geniculated, and lance-shaped.
Shell rhomboid-oval, moderately convex, solid and opaque,
not so glossy as the last species : sculpture,
numerous and
close-set flattened concentric bands, which are divided by
faintly impressed lines, so that the shell appears to be grooved
or tooled rather than ribbed these bands ;
occasionally dichotomize
or branch off, and are much stronger and more raised
(becoming laminar) on the posterior side ; they are crossed by
line, irregular, but equally numerous longitudinal strise decus-
sating the surface ; the microscopical markings are also present
: colour yellowish-white, often variegated by reddishbrown
rays, zigzag streaks, or blotches of every conceivable
width, shade, number, and form, sometimes tinged with purple,
umber, or the darkest brown, occasionally yellowish or
pure white : epidermis horncolour, fibrous, seldom persistent
in any part : margins nearly straight or but little bent in front,
trending upwards with a sharper curve to the anterior end,
which is rounded and terminated behind by an excavation for
the lunule, produced and obliquely truncate at the posterior
side, the end of which is rounded, straight and horizontal on
the dorsal side in the young but sloping gradually in the adult :
beaks small, somewhat recurved, and close to each other ; umbonal
area rather prominent : lunule lanceolate, deep but not
very distinct, nearly smooth, mostly
of a darker hue : corselet
narrow, defined on each side by the edges of the ligamental
groove : ligament rather long, yellowish -brown or horncolour,
wholly exposed and projecting beyond the lips of the corselet,
contained in a marginal groove, minutely striated across when
fractured, showing its compact
structure and tendinous tissue:
hinge-line representing a very obtuse angle : hinge-plate solid
but not very broad except under the beak, where it forms a
kind of shelf: teeth, in the right valve three erect, slender,
parallel, and nearly equal-sized cardinals, the posterior of which
is rather the smallest, and the other two are double or bifid
at the crown ; the left valve has the same number and kind
of cardinals, the anterior being the smallest, and the others
double ; laterals ridge-like and indistinct : inside towards the
beaks porcellanous, and covered with minute and irregularly
confluent tubercles, pure white or stained with purple at the