Pvn H,i I'UitlS

LUCINA. 241
on the anterior side, which joins the ventral margin at almost a
right angle, rounded in front, somewhat truncate on the posterior
side, and sometimes indented by a slight furrow running
nearly parallel with the margin to the ligamental area, which
is very gently curved : beaks small and pointed, not projecting,
slightly recurved, placed so close together as to touch, and
considerably nearer to the anterior side : lunule deep, abruptly
denned by the edges of the anterior : margin corselet, or ligamental
area, also deep and well denned : ligament very long
and straight, horncolour, sunk within the dorsal margin, but
visible outside, with the exception of a small portion on the
sides, which is overlapped by a thin layer of shell : hinge-live
representing an obtuse angle, and occupying much more than
one-third of the circumference :
hinge-plate rather broad and
strong : teeth, in the right valve one triangular and pointed
cardinal, and on each side of it a ridge-like lateral which is
raised at the end in the left valve two ;
cardinals, one of which
is much smaller than the other, the laterals being less distinct
than in the other valve : inside nacreous and partly iridescent,
salmoncoloured in the centre ; margin bevelled off and plain :
scars large and distinct. L. 0-85. B. 1.
Yar. minor. Shell smaller and flatter, with stronger and
more regular ridges.
Habitat :
A
muddy and gravelly bottom, from 8 to
90 fathoms, on nearly all our coasts, but locally distri-
buted. It is much more common in the west of Scot-
land and Ireland than it is on the southern coasts of
England. Captain Beechey dredged
it in 145 fathoms
off the Mull of Galloway. The variety occurs in deep
water off Shetland ; and there is a remarkable coinci-
dence in size between it and the southern specimens.
The geographical range of L. spinifera extends from
Nordland to the iEgean and Canary Isles. It occurs in
the upper miocene tertiaries of the South of France.
Scotch and Irish specimens are far larger than those
from the south of England and the Mediterranean.
Young shells are exquisite objects, with their snowwhite
complexion, occasionally suffused with
M
a pale