Pvn H,i I'UitlS

CARDIUM. 285
145 fathoms off the Mull of Galloway. At Guernsey
it is gregarious in 15-20 fathoms. Var. 1. Hebrides
and Shetland. Var. 2. Guernsey, 18 fathoms. The
typical form occurs, according to Searles Wood, in the
Red and Coralline Crag. Loven and manv others have
recorded it as Scandinavian and inhabiting various
depths from 3 to 100 fathoms ;
I have found it at Etre-
tat in the North of France, as well as at Spezzia ;
near
Cherbourg (Lamarck), Gulf of Lyons (Martin), Cannes
(Mace), Sicily (Philippi), and Vigo (M f
Andrew).
C. nodosum has probably been passed over as the
young of the common cockle (C. edule); but that species
is always more globular and produced in front, and has
much smoother ribs and less distinct and prominent
tubercles. The present species differs from C. fasciatum
in being more solid, and usually of a milk-white colour ;
the ribs are more thickly covered with tubercles ; the
beaks are nearly central; and the posterior side is not
obliquely produced, as in the last-mentioned species.
Young shells have a somewhat square outline. The
most brightly coloured specimens in my collection were
found in Guernsey, Arran Isle (Galway), and Balta
Sound. Southern specimens are more triangular than
those from the north.
In strict justice this species ought to be called roseum,
being the name given by Lamarck to the second variety,
three vears before Turton described his C. nodosum:
but it is now generally known by the latter name, and
the shell is rarely rosecolour. I before observed that
Montagu's shell of the same name (to
which Turton
of C.
erroneously referred this species) is the young
tuberculatum. The C. roseum of Chemnitz is a Cardissa.
C. punctatum of Philippi (but not of Brocchi) appears to
be a variety of our species.