Pvn H,i I'UitlS

304 CYPRINIDJE.
latitude, which were submerged during a comparatively
recent geological period ; and they attest the extent of
its diffusion in the glacial epoch. Other species occur
in tertiary strata of an older formation ;
and the history
of the genus, according to Mr. Searles Wood, may perhaps
date back from the Greensand.
This genus was called Arctica by Schumacher, and
Cardia, Nympha, and Asmidia by
other authors.
Cyprina Islan'dica *, Linne.
Venus Islandica, Linn. Syst. Nat. p. 1131. C. Islandica, F. & H. i. p. 441,
pi. xxix, and (animal) pi. M. f. 4.
Body yellowish -white : mantle powdered for some depth
with minute red-brown sandy points ; margin thickened, and
marked with a slender brown line : tubes nearly sessile, tinged
with red-brown ; each orifice is encircled at the base of the
cirri which fringe it with a narrow bright red line, varying in
intensity of colour ; cirri simple, about 20 surrounding the
incurrent, and about half that number the excurrent tube ;
from the latter tube frequently protrudes a globular, trans-
membranous valve :
parent, gills pale brown, unequal, coarsely
pectinated, the outer leaflets more triangular and smaller than
of moderate
the inner : palps two on each side, pectinated,
length, triangular and pointed : foot
crum, rather long and sharply pointed.
thick at the stalk or ful-
Shell obliquely triangtdar, gibbous towards the beaks,
numerous fine laminar and
thick, rather : glossy sculpture,
slightly undulating concentric striae, which become coarser and
more irregular at the sides : colour yellowish-white faintly
tinged with pink : epidermis chestnut passing into dark brown,
of a lighter cast or sometimes yellowish with a prismatic hue
in the young ;
laminar strise : margins curved in front and at the anterior
si'ie, obliquely truncate at the lower posterior end, and on
that side bluntly angular, with an indistinct fold or flexure,
which is more observable in immature : specimens beaks con-
it is marked, like the surface of the shell, with
siderably recurved : ligament strong and raised, horncolour or
dark brown, partly enclosed in a groove on the dorsal edge :
hinge-line obtusely angular : hinge-plate thick, broad, and
* Icelandic.