Pvn H,i I'UitlS

320 cyprinidjE.
coarsely fibrous. The margin is usually, but not always
notched ; and as this is the only particular in which the
CYassina depressa of Brown appears to differ from
Forbes' s species, they are probably the same. The
name given by Brown is much prior to the other. I
believe that in its young state it is the A. crebrilirata of
Searles Wood from the Red Crag.
A. borealis, Chemnitz, which rejoices in the various
synonyms of corrugata, arctica, lactea, semisulcata
(Leach), islandica, cyprinoides, veneriformis,
and com-
pressa (Macgillivray), besides several other designations
added by palaeontologists, is also a native of bigh-
northern latitudes, but not of our own seas. Imperfect
specimens have been dredged in the Hebrides, Moray
Firth, and on both sides of Shetland. It is a common
newer pliocene fossil, and found in every glacial deposit.
The most southern known limit of its habitation is Kiel
Bay in the Baltic. The shape of this shell is angular
and nearly flat ; the surface is smooth, or faintly striated
in the line of growth, except towards the beaks, where
there are several fine concentric ribs ;
and the epidermis
is coarsely fibrous as in A. crebricostata or depressa.
It attains a larger size than that shell. The occur-
rence t)f the last two species in our seas, in a semifossil
state, may be accounted for in the same way
Pecten Islandicus, page 58.
as that of
A. eastanea of Say, a North-American shell, has been
called British without any sufficient reason. It is the
Venus sulcata of Montagu, as well as of Maton and
Rackett. Mr. J. Sowerby gave a specimen as " English"
to the former; and Mr. Swainson informed the latter
that he received one from the Duchess of Portland, also
as "English," and moreover that the shell had since
been found in the north of Scotland, where it was known