‘
BORIN‘G‘LIFE
_
I‘49
rarer
rock—boring mOllüscs of '
which perha‘péëtbe
interesting is Petm'aola. phol—adÿ‘ormäs which, î'thOugh “ it
'
.
belongs to a family of bivâlves ”far
from "
the
Piddocks, has come, “pas ta result…of Fits similar habit éof
life, to resemble'îthese
The
‘
commonest of all, took
smaller :mollüsC; never
more than about one inch
5
Which is
aïbundat
i‘n‘ shalloW
rocks; of…—t‘en ‘_in —
those of such
that'sd
comparatively«delicae
exCavated the
burrows. __It is; probable that ai;
a: cèr‘ta‘ihmo1int
of ’
_the borig »is= per£ormed by cheiical 3means, ”although”
this «animal is alsofoun‘d=in rocks, such-‘as‘Sandsïon-a
chemical actibh;wouldhe nnàv‘ailiüg. Ne espeCiat—l glands
for the
ier” eating awày—the‘rock have
been discovered
either*îSædcaäza*or’the'PiddbckS’but it
'
‘
may be that, the ;:ESQÏtï …13arts”off the body ’ Which project
beyond the shell may eXerci$e:æSolventaction of some kind.
There iSz,0_e rock ‘b®î‘6tg‘Whiä3h ni1doùb‘tedly‘ makes its
EtThis 'is' the Date—mussel
'
Jseas, îso called because
of its
shape, to "the date.“
_
.
müsSel. ' 'The "brown,
is due to the presence «of a
th1ckhomy1ayerover ä;he«suace of‘the shell, Which is itself
VGÎY
of teeth Or spines. It always
'
rows in rmnestqne‘m
Calcareous rock {Plate 56),
B0t
action of thedelicate shell but by the aid of an
acid
by“-a special gland in the soft
-
tisSues
the shell.
Acid attacks calcareous'
matter very-readily but—not other forms of rock and this
,
is the -'èXplanation of the “invariable preference of the Date;
'
muSsel for calcareous rocks.
The shell, Of course, is also