THE SEA'SHORE
33
which may be several inches thickand vary' in colour from
a pure white in shaded places t0'- a yellow or green‘in more
exposed situations.
The deep crims0n Hymeniacidon is
—
often found with it.‘
À common spor1gè Which—is attached
by a stalk is the purse sponge (Grantia Compressà); biten:
found on the sides of rocks where there
danger of
it being dried up, and there are Other kinds of sponges‘ too
numerous to describe.
Growing “on rocks or fucoid fronds
is the tiny worm
which lives in a at spiral shell
like that of a snail and often occurs in great numbers;
—
Larger worms with limy tubes of irregular shape (Serpulids)‘
are
frequently common on rocks.
Frequently eovering
rocks are found sea squirts, especially the compound
_
consisting "of colonies of simple individuals—sùèh as the
golden-stars Tunicate (Botryllus), which cloSely resembles
a sheet of purple jellîy dotted_ with tiny golden stars (Plate 12)
'
,
though some simple sea squirts are found-, especially the—
'
Goo“seberry _(Styleopsis grossulaa), a little reddish lump'
well described by its oommonÎname,ï and
near
Ü
low—water mark (Plate 12).—
Other encrusting animals ‘arethe sea mats or polyzoa; Which form, withthe
squirtS,- coralline Weeds and other algæ, a dense carpet
over the face of the rocks.
Finallÿ about low-water mark
we
may _nd—biValve
molluscs5such as the saddlé—oyster
(A nomia), the common mussel _(Myiz‘lus edulis) and one of
the smaller scallops-‘such as=Pectenr vañu’s; ‘ These' are
attached in different Ways; the saddle—“oÿSt‘er being per—
'
manently attached by its shell and adhering
tothe surface of the stone1whe
musæl 'and scallop‘ are
secured by to'ugh threadskùown as ‘5 byssus
”
the
formation
'
-
of which is described on
'
_…
'
'
A fresh fauna is revealed when we begin to turn over loOse
7 stones.
Near high-water mark-there is a varied collectiOn
of small crustaceans and insectS.-‘ "Of the former the largest