40
THE SEAS
is frequently mixed, burrowing forms being by far the
commonest.
Thus, of the bivalves, the large
“
gaper,"
Mya truncata, is the most conspicuous, it possesses & thick
shell—some three times the size
mussel—Which has
a permanent gape at the bind end where the long, muscular
-
.
"
siphons project (Fig. _4).
Another
,
characteristic type is Scrobicularia, to
.
be recognized by its extraordinarily
'.
'
attened shell and by the length of the '
=
siphonswhich,unlikethoseof the gaper,
,
—
are
free from one
another.
Where
—
the inud is iintermingled ”with stones
'
the large horse-mussel (Modiolus) is
'
common.
Worms are abundant, es_
«&
pecially burro'wing species, and those
‘
living in tubes ; Îof these the common
'
Sabella
pavom'na, with its rubberlike tube and widely spread ring of
-
.
red and white plumy tentaCles, and
'
Mym‘cola infundz‘bùlum, with its thick
gelatinous tube and shorter, more com—’
pact tentacles, are the commonest.
_
,
»
The former often occurs in such num-'
j bers that at low water the ”tubes, of
—
'
»
which usually some ve inches project
.
-
_
above the surface, appear like a little
' _
.
forest.
Of
anemones,
the
brown
’
FIG- 4-—The 58?“
.
—
bellis
is
the
commonest.
’
(Mya truncaia),
_
.
'
‘
There are a variety of crustaceans
including the ubiquitous scavenging shore crab. Estuaes
and creeks with a mixed bott0m of mud and stones often
harbour oysters,’which are fastened to the stones, and—with
these are;found.their 'invarià.ble ene'mies; the boririg dog'
whelks, NasSa and Murex and the common. starsh, Asterids