the HS TP 0. RY of ci N.S EOC mS: 
, Thefe thell-fith are found very numerous on 
the thelves or fand banks near the fea, where 
the mutcles are alfo found, and among the latter 
they are frequently fold; but they have alfo pe- 
culiar and proper places; in the fea, where they 
ftick together in large heaps. I have fometimes 
taken them from the piles of timber, on which 
they are often fixed in the fea, and fometimes 
I have pulled them from large willow ftumps, 
which were formerly laid on the fhore, to 
break the violence of the waves ; between thefe 
ftumps, and among {tones, are fometimes found 
many other rare water infects, as the Pulmo 
Marinus, or Sea Lungs, the Urtica Marina, or 
Sea Nettle, a fpecies of the Echinus, the Stella, 
or Star-fith, Tubuli, or Sea Worms, Afelli 
Marini, Sea Wood-lice, and others. The ma- 
ritime coaft of Holland is the only place I 
know wherein one can make thefe ufeful ob- 
fervations, for all other coafts in general are 
{mooth and plain, or covered even with fand. | 
_ That this fhell fifh may be better known, I 
fhall firft defcribe its external, and then its in- 
ternal parts. Among the external parts I reckon 
the fhell, which is the ftony skin of this Snail, 
as well as of all other infects that inhabit thells, 
it is on the outfide invefted with a periofteum, 
which appears very beautiful in young ones, 
becaufe no part of the fhell has been in them 
worn out or rubbed off. Underneath, where 
this Snail, Tab. IX. fig. x1v. a, creeps out of the 
mouth, the door or entrance of its fhell, the 
latter is a little globular 4, but it lofes this figure 
by degrees, after it is rolled five times, 1,2, 3,4, 
5, and is terminated ina fharp point. The 
external furface of this fhell is rough and une- 
qual, fince from its mouth or entrance to its 
acute end, it is folded and curled with thirty- 
one little ribs or furrows; which appear like fo 
many threads above the furface c. I have not 
met with this exact appearance in all of them, 
as it feems in many to be worn out and oblite- 
rated with age; for the older ones have po- 
lithed fhells, and are divided, fig. xv. d, only by 
fome rings or wreaths of divers forms and co- 
tours ; unlefs thefe thells may probably belong 
rather to another particular {pecies, which I 
think is moft probable. As to the colour of 
the fhells, it is a light red in the former {pecies, 
but in the other it is mixed with green and 
afh-gray. and fometimes red, purple, blue, or 
whitifh. ‘The internal furface of the thell is 
all equal and {mooth, it is of a dark brown in 
both fpecies, fomewhat inclinable to a bluith 
urple. 
The fhells of thefe Snails are frequently eaten 
through, by fome of the largeft Sea Worms *, 
as may be feen particularly in the upper or 
pointed extremity, for it is frequently found 
gnawed there in confiderable holes, in fuch a 
manner, that the whole figure of the fhell is 
obliterated in that part; nay, I found from 
* This is a common accident to fhell fifh: not only worms gnaw the fhells, 
kind of bony engine, with which they pierce the hells, 
foffil fhells were real, or exuvie of animals, 
earth thus pierced by Pholades, 
Br 
experience, that thofe worms fometimes per- 
forate into the inward texture of the fhell, and 
there form various crooked and oblong hollows; 
Tab. IX. fig. xv. e, which fometimes penetrate 
into the cavity itfelf, fothat the Snail is obliged 
to draw up the hinder parts of its body. 
I have found feven fuch Worms in one hell; 
the Snail whereof was ftill living and unhurt. 
I here exhibit one of thefe Worms, fig. xvt. a, 
if this Worm be viewed with a microfcope, it 
is found to confift of many annular incifions; 
which are adorned, fig. xvi1. ¢c, with {mall 
hairs on each fide ; in the middle are feen two 
veins of a bloody colour, which extend their 
little branches on either fide towards the inter- 
fections of the body. In the fore part of its head 
a are alfo fome hairs, which are placed there 
like antenne or horns: the like 4 are feen alfo 
at the tail. All thefe Worms had a very thin 
skin.; they were of a tender conftitution, and 
moved but very little. Whether this might have 
proceeded from my hurting them, by ftriking 
them with a hammer, or was natural to them, 
I cannot fay. In the foulnefs which adheres to 
Oyfters, I faw a {pecies of larger worms, which 
were not in figure very unlike this {maller kind; 
and, like the Glow-worm, fhined in the dark. 
All thefe fhell fith feem to be fubje& to this 
Worm as a difeafe, fince few of them are 
met with, whofe fhells are entire and found 
at the end of their convolutions or windings ; 
for the fhells are always invefted there with 
a dirty or filthy afh coloured fubftance, where- 
with they are more or lefs infected, and in 
which thefe worms feem by degrees to fix 
themfelves, fo that at length they feize on the 
fkin of the thell fith, as their proper habitation 
and food, though the Snail ftill continues to 
live in it. This fhell has very hard and folid 
joints, as appears in its fpiral pillar, which is 
likewife very thick; hence it is that the Snail 
may be eafily difengaged from it, fince the thell 
flies in pieces like a flint, if it be {truck ever fo 
lightly with a hammer. 
The body of the Snail, which creeps out 
of this fhell, but is by its mufcles very ftrongly 
annexed to the pillar of it; the head and 
mouth, Tab. IX. fig. xvii. a, are nearly like 
the Snails, and fo are the horns 4 4, and eyes cc: 
The colouring of the fkin only differs, for it 
is variegated with black furrows and {pots on a 
white ground: in regard however to the colour 
of the two fpecies, there is fome difference to 
be obferved. Behind, at the verge of the bo- 
dy dd, is the Snail’s operculum or cover e; which 
it fuddenly draws in at pleafure, and by this 
means fhuts up its fhell, when it meets with 
any thing unufual: the creature provides for its 
fafety in the fame manner, when any thing 
is f{uddenly prefented to its eyes ; fo that I may 
venture to affirm from hence, that this is the 
only fpecies of Snails that I know, wherein any 
but the large fhell fith of fome kinds have a 
to get at the creature for their food. When it was doubted, whethed 
or reprefentations of them, from the {portings of nature, fhells taken out of the 
were produced, and the objeétions ceafed: 
mantfeft 
