Pvn H,i I'UitlS

CYPRIXID.E. 297
of W. Wood (C serratum, Turton), and C. Graznlandicum
of Chemnitz (C. edentulum, Montagu, and Mactra
radiata, Donovan) are not British, although they have
been wrongly introduced into our fauna. The first
three are tropical, and the last arctic. Dr. Fleming
was mistaken in regarding the C. nodosum of Turton as
the young of C. muricatum.
Family XII. CYPRI'NID^, Geinitz.
Body globose or suborbicular : mantle open in front : tubes
sessile or short :
gills nearly equal in size : foot tongue-shaped,
and adapted for burrowing in sand or mud.
Shell equiyalve, globose or rounded, with a triangular out-
line, more or less equilateral, solid, concentrically
striated or
furrowed : beaks twisted spirally or turned to one side : ligament
mostly external : hinge short but strong, furnished with
two or three cardinal teeth, besides laterals, in each valve ;
pallial scar entire : muscular scars oval and usually very distinct.
This family holds a middle rank between the Car-
diidce and Veneridce, but is more nearly allied to the
latter. It differs from Cardiidce principally in the shell
not having the longitudinal ribs which characterize that
family, and from Veneridce in the tubes of the animal
being sessile or short, and in the pallial scar being con-
sequently entire at the posterior side. I am not quite
satisfied, however, that it is a " good " family, except as
regards the single genus Isocardia.
All the Cyprinidce are inhabitants of sandy and muddy
tracts of the sea-bed. Thev mav, on the whole, be re-
garded
as northern forms.
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