Pvn H,i I'UitlS

at their extremities ;
VENUS. 345
both have at their orifices fine red-brown
cirri, which in the branchial tube are alternately longer and
shorter :
gills suboval, pale brown : palps triangular, striated
more distinctly on the inner than on the outer surface : foot
pure white, rather thick, slightly bent at the heel.
Shell triangular, rather convex, solid and opaque, more
glossy in young than in old :
examples sculpture, regularly
imbricated concentric ribs, which vary much in number and
fineness, the course of imbrication being backward ; they are
now and then forked or become divided towards the posterior
end, and are crowded at each side and in front ; the whole
surface is also covered with extremely numerous and delicate
longitudinal striae which are only perceptible
with the aid of
a strong magnifier : colour pale yellowish-white, usually va-
riegated bv three reddish-brown longitudinal ravs of dif-
ferent widths, composed
of numerous and short broken streaks
or spots of the same tint, which sometimes cover the whole
of the shell and give it a beautifully stippled (or now and
then a vandyked) appearance ; occasionally
gated, nor are there any coloured markings
it is not varie-
on the funda-
mental hue: epidermis extremely slight, only present on the
corselet and in young specimens : margins obliquely rounded
in front, curved upwards on the anterior side, and forming an
obtuse angle at that extremity in consequence of the excava-
tion of the lunule, produced and wedge-shaped on the posterior
side, which is somewhat flexuous and confined by an
acute angle formed by a junction with a long and nearly
straight slope on the dorsal side : leaks small, recurved and
separated ; umbonal area : prominent Ivnule varying in shape
from cordate to lanceolate, rather deep and defined by a distinct
groove, longitudinally striated, sometimes tinged with
reddish-brown ; lips flexuous, much : projecting corselet broad
and somewhat deep, with shelving sides, obliquely striated :
: ligament narrow, yellowish-brown, wholly exposed hinge-line
obtusely angular :
hinge-plate thick, broad, and flexuous : teeth,
in the right valve three divergent cardinals, the middle one
being somewhat conical and by far the thickest, the anterior
is the smallest but a little higher than the others, and the
posterior is very long, slight, laminar, and sometimes double ;
the left valve has also three cardinals nearly corresponding in
size and position with those in the opposite valve ; laterals
sometimes distinct, being apparently formed by the extension
of a ridge, which runs on the dorsal slope outside the posterior
q 5