Pvn H,i I'UitlS

LIJCINA. 243
rior side, which is indented by an indistinct furrow running
nearly parallel with the ligamental area : beaks very
small and
pointed, rather prominent, much recurved, almost contiguous,
and ex-
considerably nearer to the anterior side : lunule deep
cavated : corselet level : ligament very long and straight, yel-
lowish-brown, seniicylindrical, slightly projecting outside ; its
sides are covered by a shelly strip, which is usually found
broken in small pieces by the action of closing the valves :
hinge-line curved, occupying not quite
one-third of the circum-
ference : hinge-plate broad and thick : teeth, in the right valve
two strong cardinals, the anterior one being double, and the
posterior much smaller and set more obliquely,
and on each
side of the beak a plate-like lateral, the anterior one being
slightly raised at the end, and the posterior much longer than
the other in ; the left valve two similar cardinals, but nearly
of equal height, and corresponding laterals : inside chalkywhite,
but in places irregularly tubercular from an internal
deposit of nacre : margins bevelled off and plain, sometimes
grooved longitudinally : sears remarkably large and distinct.
L. 1-4. B. 1-5.
Yar. 1. depressa. Shell natter and thinner, with fewer ribs
and the beaks less prominent.
Yar. 2. gibba. Shell much smaller, with a more oblique
outline, the valves protuberant, ribs closer together, epidermis
iridescent, and the beaks more prominent. L. 0-45.
B.05.
Habitat :
On
all our coasts, in muddy gravel and sand,
from the low-water mark of spring tides to 82 fathoms.
Captain Beechey has dredged
it off the Mull of Gallo-
way in 110-145 fathoms. The late Wm. Thompson and
II . Ball found it in lakes of brackish water at Arran.
Dr. Lukis informed me that this species was comparatively
rare in the Channel Isles, and that the numerical
proportion which it bore there to Loripes
lacteus was as
1 to 50. He added, " Lucina borealis was wrongly stated
by Forbes and Hanley (vol. ii. p. 48)
to occur '
abun-
dantly near St. Peter's Port in Guernsey/ We do not
meet with it excepting at Herm. I have never found a
single specimen on the Guernsey coast, although
m 2
I have