Pvn H,i I'UitlS

MYTILUS. 115
f
side incurved, and dorsal side arched instead of being angu-
lated.
Monstr. Upper valve nearly flat and much smaller than the
other.
Habitat : Not uncommon on the southern and west-
ern coasts of England, Wales, and Ireland, and found
by Mr. Bean at Scarborough, on rocky and stony ground,
from low-water mark to 18 fathoms. Var. Portsmouth
(J. G. J.). Monstr. South Devon (Mus. Loscombe).
This species is a Red Crag fossil. It has not been re-
corded from any place north of England; but its south-
ern range extends to the iEgean and Algeria.
According to Mr. Clark the "
gills entirely coast the
body, being brought close to the posterior extremity to
receive the water. This structure of the branchiae is
the substitute for the absence of tubes or any sort of
siphonal fold of the mantle." The shaggy
beard of the
shell is very peculiar. Montagu says that it is partly
owing to the epidermis being broken and divided into
fibres; and he also observes that, while in a soft and
glutinous state, it arrests such extraneous matter as
comes in contact. Gould suspected that the epidermis
but he evidently had not then
was a parasitic vegetable ;
had an opportunity of seeing it. The byssus resembles
a bundle of fine tow. M. barbatus differs from the young
of M. modiolus in the shell being narrower at the an-
terior and much broader in proportion at the posterior,
side, as well as in the angularity of the dorsal margin,
straight hinge-line, strong laminar ridges, reddish colour,
and the epidermis being serrated or barbed on one side
instead of being plain as in that species.
This species does not appear to inhabit the north of
Europe, unless it is the shell noticed by
'
Zoologia Danica •
as
Muller in his
smaller than M. modiolus, with a