Pvn H,i I'UitlS

282 CARDIID.E.
Yar. 1. globosa.
being less produced.
Shell more globular, the posterior side
Yar. 2. alba. Shell milk-white, of an intermediate shape
between that of the typical kind and the first variety.
Habitat :
Gravelly sand, in 5-90 fathoms, from Shet-
land to the Channel Isles, generally diffused and rather
common. Var. 1, Shetland and west coast of Scotland.
Var. 2. Off Unst in deep water, together
with coloured
specimens. In a fossil state this species occurs in the
Clyde beds at Bute (Smith) ; Coralline Crag (J. G. J.) .
Its foreign range extends from Iceland (Steenstrup and
and Sweden
Torell), Faroe Isles (Morch), Norway
(Loven, Sars, and others), Bay of Kiel (Meyer and
Mobius), Zealand (Hsellebsek), Cannes (Mace), Spezzia
in 18 fathoms (J. G. J.), Gulf of Tunis, Malaga, and
Canary Isles (M'Andrew), to the Azores (H. Drouet).
In Finmark it acquires a comparatively enormous size.
It is one of the Uddevalla fossils.
This shell is never sharply angular like C. exiguum,
and it is of a much thinner substance. In the young
the prickles
are vaulted, and cover the ribs in the same
as brick tiles are set on the crest of a roof. The
way
fry are almost flat, and have a square contour. They
may be distinguished in this state from C. exiguum by
having more ribs. Mr. Clark observed a specimen to
be full of ova on the 4th of August.
Owing to the posterior side being more produced in
some specimens than in others, Montagu seems to have
made two species out of this one, viz. C. elongatum and
C. fasciatum. The former represents the more usual or
typical kind. I have a shell which was sent by Mr.
Dillwyn to Col. Montagu for his opinion, and returned
with the name " Car. fasciatum " in the handwriting of
the latter on the cover of the small packet which still