34 
CONCH 
ends; the hinge has a tooth fliaped like an awl, bent back, 
often double, and not inferted, into the opposite (hell: 
the rim at - the ildes appears fomewhat worn away, and 
lias a horny cartilaginous articulation. Three of them, 
the fdiqua, vagina, and crifpus, are found among the land 
on the Britjfh coaft, and generally in an ere6l or perpen¬ 
dicular direction. The fifh has two pipes, -each corrrpofed 
of four or five rings or portions of a hollow cylinder, of 
unequal lengths, joined one to another; and the places 
where they join are marked by fine ftreaks or rays. Of 
this genus there are twenty-three fpecies, the raoft prized 
of .which is the radiatus. This (hell is of a light violet 
ground, with liivery white rays, diverging from the hinge 
to each, extremity, fomewhat refembiing the fun when 
Alining through the clouds, and, what is vulgarly called, 
'drawing water. This knife-handle is very rare, and found 
only in the Indian ocean. 
PINNA, or Sea-wing. —The pinnae, fea-wings or hams, 
: are fhells of a fomewhat triangular fhape, widening from 
a pointed or narrow top to a very broad end, which broad 
•end is always open. The hinge is inarticulate, or hinge 
without a tooth. The animal this fhell intlofe 4 is a kind 
of ftug. The fhell is fragile, and furnifhed with a beard. 
Thefe are found on fome parts of the coufis of France, 
Italy, and the Indian ocean. The iargeft and moll re¬ 
markable are found in the Mediterranean. The animal 
is blind, as are all of the genus ; which confifts of eighteen 
fpecies. It is furnifhed with very ftrong calcareous valves; 
■and they have the faculty of attaching themfelves firmly 
to the rocks. Thefe fhells are often valuable, on account 
of producing many beautiful pearls. Thofe moll prized 
by conchologiiis are the pinna muricata, rotundala, and 
iiobilis. 
OF MULTIVALVES, OR SHELLS OF MANY PARTS. 
The third general divifion ofteltaceous animals is into 
multivalves, or thofe fhells that are made up of many 
diltindl pieces. There are three families in this divifion, 
viz. i. Pholas, the piddock. 2. Lepas, the barnacle and 
acorn (hell. 3. Chiton, the ofeabrion. 
. PHOLAS, the piddock.—Thefe fhells are trivalves, 
having two. large valves, with a fmall valve placed be¬ 
tween them, near to the hinge. The hinge turns up on 
the outer part of the fhell, and under it, within the fhell, 
is a long curved tooth or fpur. The word pholas is de¬ 
rived from the Greek, and fignifi.es fome thing which lies 
hid. This name they derive from their property of 
making themfelves holes in the eaith, fand, wood, or 
Tone, and living in them. The means of their getting 
there, however, are as yet entirely unknown. All that 
we can with certainty fuppole, is, that they mull have 
penetrated thefe fubftances when very fmall; becaule the 
.entrance of the ho’ in which the pholas lodges, is always 
much lefs than the interior part of it, and, indeed, than 
the (hell itfelf. Hence fome have fuppofed that they were 
hatched in holes accidentally formed in ltones, and that 
they naturally grew of fuch a fhape as was necefl'ary to fill 
up the cavity. 
The holes in which the pholades lodge, are ufually 
twice as deep as the fhells are long; the figure of the 
holes is that of a truncated cone, excepting that they are 
terminated at the bottom by a rounded cavity, and their 
pofition is ufually fomewhat oblique to the horizon. The 
openings of thefe holes are what betray the pholas being 
in the lfone; but they are always very fmall in propor¬ 
tion to the fize of the fhell. There feems to be no pro- 
greffive motion of any animal in nature fo flow as that of 
the pholas ; it is immerfed in the hole, and has no move¬ 
ment, except a fmall one downwards, and this is only pro¬ 
portioned to the growth of the animal. Its work is very 
difficult in its motion; but it has great time to peiform 
it in, as it only finks itfelf deeper in the itone as it in- 
creafes in bulk. That part by means of which it performs 
this operation, is a flefhy lubftance placed at the lower 
extremity or the fheil; it is of the fhape of two points or 
O L O G Y. 
claws turned towards each other, and is confiderably large 
in proportion to the fize of the animal; and though it be 
of a loft fu bit a uce, it is not to be wondered that in io lorn; 
a time it is able, by conftant wrnrk, to burrow into a hard 
(tone. The manner of their performing this may be feen 
by taking one of them out of the Itone, and placing it 
upon fome loft clay; for they will immediately go to 
work in bending and extending that part allotted to dig 
for them; and in a few hours they will bury themfelves 
in the mud in as large a hole 4 s they had taken many 
years to make in the (tone. They find little refiftance in 
fo foft a lubftance ; and the, neceffity they feel for hiding 
themfelves evidently makes them haften their work. The 
body of the animal is lodged in the lower half of the hole 
in the (tone, and the upper half is occupied by a trunk of 
a flefhy fubilance and conical figure; this they ufually 
extend to the orifice of the hole, which doles or crults 
over, fo as to leave the point or top of this inftrument 
naked or bare. This trunk, though it appears Angle, 
is, in reality, compofed of two tubes, or at lead it is com- 
pofed of two parts feparated by a membrane. The arti¬ 
fice of this double inftrument is fimiiar to that in many 
other ftiell-fifh, namely, to take in fea-w’ater by one tube, 
and, when digelfed, to rejeff it by the other. "This trun¬ 
cated flefhy inftrument is ufually about five inches long, 
and from the fimilarily of its appearance, has acquired 
to this fifh the trivial name of the fea-penis. In the mid¬ 
dle of their bodies they have a fmall green veficie, the ufe 
of which has not yet been difcovered. This, when plunged 
in fpirit of wine, becomes of.a purple colour: but its co¬ 
lour on linen will not become purple in the fun like that 
of the murex; and even if it would, its quantity is too 
fmall to make it worth preferving. 
The pholas fhell, as well as the included animal, is re¬ 
markable for its luminous quality. T hat the fifh is lu¬ 
minous, was noticed by Pliny, who obferves that it fliines. 
in the mouth of the perlon who eats it; and if it touch 
his hands or clothes, it makes them luminous. He alfo 
fays that the light depends upon its moifture. The light 
of this fifti has furnifhed matter for various obfervations 
and experiments to M. Reaumur and the Bolognian aca¬ 
demicians, efpecially Beccarius, who took fo much pains 
with the fubje-ft of phofphoreal light. M. Reaumur ob¬ 
ferves, that whereas other fifties give light when they 
tend to putrefcence, this is more luminous in proportion 
to its being frefh ; that when they are dried, their light 
will revive if they be moiftened either with frefh or lalt 
water, but that brandy immediately exlingu.fhes it. He 
endeavoured to make this light permanent, but none of 
his labours fucceeded. 
The attention of the Bolognian academicians was en¬ 
gaged to this fubjefft by M. F. Marfilius, in 3724, who 
brought a number of thefe flieli-fiflies, and the ftpnes in 
which they were inclofed, to Bdlogna, oft purpofe for 
their examination. Beccarius obferved, that though this 
fifti ceafed to fliine when it became putrid, yet that in its 
moft putrid ftate it would fliine, and make the water in 
which it was immerfed luminous, when it was agitated. 
Galeatius and Montius found that wine or vinegar ex- 
tinguifhed this light; that in common oil it-continued 
fome days ; but, in rectified fpirit of v.'ine or urine, it ex- 
ifted hardly a minute. In order to obferve in what man¬ 
ner this light was affe< 5 ted by different degrees of heat, 
they made ufe of a Reaumur’s thermometer, and found 
that w'ater rendered luminous by thefe fifties increafed in 
light till the heat arrived to forty-five degrees ; but that 
it then became fuddenly extinct, and could not be re¬ 
vived again. In thefe experiments of Beccarius, a folu- 
tion of iea-falt increafed the light of the luminous water ; 
a folution of nitre did not increafe it quite fo much. Sal- 
ammoniac dimini(b.ed it a little, oil of tartar per ddtquiu/n 
nearly extinguiflied it, and the acids entirely. This water 
poured upon frefti calcined gyplum, rock ciyftai, cerute, 
or fugar, became more luminous. He alfo tried the ef¬ 
fects of it when poured upon various other fubftances; 
but 
