Pvn H,i I'UitlS

180 ARCID/E.
certainly not that of Linne. Pennant made the same
mistake. It has had many other names, including
Mytilus Garnseice (Petiver), A. crinita (Pulteney), A,
Gaimardii and A. Quoyii (Payraudeau), A, striata
(Reeve), and A. Pennantiana (Leach).
I found a small single valve of A. nodulosa, Miiller,
in some dredged sand from Shetland. This species in-
habits the Swedish and Norwegian coasts, and occurs
at depths varying from 15 to 150 fathoms. The shell
is broader or more produced at each end, and thinner
than that of A. lactea ;
longitudinal
of cross ribs ;
the sculpture consists of several
rows of vaulted or imbricated scales instead
and the teeth are not half so many as in
the other species, and they are placed more obliquely or
diagonally. It is closely allied to A. imbricata, but in
that species the inside margin is notched. A, aspera,
Philippi, from the Sicilian tertiaries, appears
same as Midler's species.
4. A. tetrago'na *, Poli.
to be the
A. tetragona, Poli, Test. Sic. ii. p. 137, t.25. f. 12, 13; F.&H. ii. p. 234,
pi. xlv. f. 9, 10, and (animal) pi. P. f. 1.
Body white : mantle having its border plain, but the upper
half of it on the posterior side is fringed with about 40 close-
set and equidistant ocelli or dark dots, which vanish or are in-
distinct towards the anterior side the ; margin is also mottled,
both above and below, with flakes of :
«pale yellow gills nearly
coequal in size, and striated, of a brown colour :
lips expanded,
formed out of the extremities of the gills : foot white
and subconical, tapering to a blunt point,
a deep byssal groove : byssus dark-green, composed
leaf-like plates.
and furnished with
of a few
Shell forming an irregular parallelopipedon, and angular,
sometimes twisted on the posterior side, very tumid, solid, of
a dull hue : sculpture, the same as in the last : species colour
* Quadrangular.