Pvn H,i I'UitlS

LEPTON. 195
compressed and almost flat, thin, seniitransparent and glossy :
sculpture, numerous and minute circular pit-marks,
which are
caused by the intersection of a close network of fine longitudinal
and transverse ribs, the former radiating from the beaks
and curved towards the back and sides ; there are also distinct
lines of growth, which vary in their distance from each other :
colour snow-white : epidermis exceedingly thin, and only
shown by an iridescent hue in : young specimens margins
obliquely
truncate on both sides, with the angles rounded, somewhat
incurved in front, and slightly curved outwards at the
•back : beaks small, somewhat prominent, placed a little nearer
to the anterior than to the posterior side :
hinge-line gently
curved, occupying nearly one-third of the circumference of the
close to the beaks
shell : cartilage triangular, yellowish-brown,
on the posterior side : hinge-plate broad, incurved, excavated
in the middle for the reception of the : cartilage teeth, one
small and slight but upright cardinal, lying directly under the
beak and close to the cartilage, and a long laminar lateral on
each side of the cavity containing the cartilage ; the lateral
teeth are placed at a little distance within the hinge -line :
side iridescent, striated lengthwise but irregularly ; margin
plain : pallial and muscular scars usually indistinct, owing to
the thin texture of the shell. L. 0-575. B. 0-45.
Habitat :
in-
Shelly gravel and sand, in 8-20 fathoms,
on the coasts of Cornwall, Devon, and Dorset,
as well as
at Guernsey, and in the south and west of Ireland. It
is recorded in the '
British Mollusca '
as having been
found bv Lvons and Hanley at Tenbv, bv M fAndrew at
Anglesea, and by Barlee at Oban ; but another locality
there given on my authority (" off Skye ") must have
originated in a mistake. Searles "Wood found a single
specimen in the Coralline Crag at Sutton. Its foreign
range appears to be limited or little noticed. Lilljeborg
has taken it at Christiansund in Norway, Malm
and Loven on the coast of Bohuslan in Sweden (the
former in 12-20 fathoms), I found it at Etretat in Nor-
mandy, Cailliaud in the Departement of Loire-inferieure,
and M fAndrew dredged it at 8 fathoms in Vigo Bay.
It may be decidedly considered a local species.
k2