428 
M 
this fhape are fometimes found, which we're in much efti- 
mation among the ancients, and are at prefent very va¬ 
luable in the Eaft Indies. There are undoubtedly feveral 
kinds of worms which pierce the fhell, and form cavities 
more or lefs round, in which the juice confolidates into 
pearls. It is this obfervation, which has no doubt been 
made by others befides me, that probably firft fuggeited 
to forne perfons concerned in the pearl-fifhery, the trick 
of making- artificial perforations in the fhells, and thus 
forcing them to produce pearls. At London, I faw fome 
fhells brought from China, which mull have undergone 
this operation ; for the artificial hole was filled u<p with a 
piece of brafs wire, rivetted on the outlide of the Ihell 
like the head of a nail, and the part of the wire which 
pierced the interior fhinilig coat, was covered with a well- 
Ihaped pearl, which feemed as if foldered to its extremity. 
It is probable that, with the Chinefe, who have been fo 
long (killed in the arts, and whofe aftonifhing and multi¬ 
plied induftry teaches us that we are but a comparatively 
new people, this is not a difcovery of a very modern date. 
“ Brouffonet, with whom I had a converfation upon 
this fubjeft in London, at the houfe of fir Jofeph Banks, 
told me that a perfon had allured him, that there is dill 
another method of obtaining pearls. The (hell, on which 
the experiment is to be made, mull be opened with the 
greatell care, in order to prevent the animal from being 
injured. A frnall portion of the inner furface is then 
fcraped off, and in its room is inferted a lpherical piece 
<jf mother-of-pearl about the fize of a very frnall grain of 
lead-lhot. This globule ferves as a nucleus to the pearly 
juice, which concretes around it, and, at a certain dil- 
tance of time, produces a fine pearl. He faid, that expe¬ 
riments of this nature had been tried in Finland, and re¬ 
peated alfo in other countries. From thefe obfervations, 
it may be inferred that the produftion of pearls depends, 
perhaps, much more upon an external and accidental 
caule than upon a natural fuperabundance or extravaia- 
tion of the juice of which they are formed. 
“ There are very excellent pearls found in the river- 
Ihells of Loch Tay, if we may judge from fome which 
the filliers of Killin offered to lell us at more than double 
the price of thole which are in current fale. But thefe 
fine pearls are far from numerous; on the contrary, a very 
great number are found which the jewellers rejefil, but 
which, though they may be not well calculated to form 
decorations for the ladies, are yet very interelling for the 
cabinet of the naturalill, fince they afford a confirmation 
of the theory which I have now mentioned. The greater 
part of thefe pearls have little or no luftre; fome are round, 
oval, or elongated, and cylindrical; others are hemifpheri- 
cal, refemblinga button ; feveral oblong ones have a con¬ 
traction towards the middle, which gives them the appear¬ 
ance of two joined together; others alfo are fomewhat 
conical; and all are of a pretty large fize, and of a pale 
and red or browm colour. The end of the pearl touching 
the tegument of the fhell, which forms what is called mo¬ 
ther-of-pearl, is fo deeply impregnated with the fhining 
fubftance, that it exhibits a lingular contrail with the 
furrounding brown colour of the other parts, and feems 
to derive additional fplendour from it. This coating is 
of an orient bordering on rofe-colour, which is extremely 
agreeable to the eye, and is therefore heightened in its 
effeCl by the contrail. Pearls of this kind are fo feldom 
met with, that they might at firft be taken for oculated 
agates prepared for being fet, or rather for buffonites, par¬ 
ticular^ thofe which have no mother-of-pearl. Their 
texture is very hard, and yields with great difficulty to 
the file. The augur-worm, which occalions the forma¬ 
tion of the pearl's of Loch Tay, pierces the whole thick- 
nel’s of the fhell, which is of conliderable denfity and of 
a fallow brown colour ; and, as the fhelly juice oozes out 
from all parts of the orifice which the worm has formed, 
it neceffarily refults, that the pearl mull participate in the 
quality and colour of the fubftance of the fhell, from the 
exterior layer to that which lines and embellifhes its inner 
4 
Y A. 
furface. Hence originate thofe rude but fingular gems 
above-mentioned, which have only a thin coating of mo¬ 
ther-of-pearl upon one fide. There are, how'ever, fome 
inftances in which the pearl is pure and brilliant through¬ 
out; proceeding probably from an extravafation of the 
interior coating only ; which may have been occafioned 
•by another kind of augur-worm attacking the fhell folely 
in the direction of that coating. It is the province of 
thofe naturalifts, whofe attention it has more particularly 
engaged, to inveftigate more profoundly this very interell- 
ing lubjeft, our knowdedge of which mull yet be confi- 
dered as nothing more than a rude outline.” 
_ 5. Mya margaritifera, the true pearl-oyfter. This fpe- 
cies has been fully deferibed under the article Concho- 
logy, vol. v. p. 33. 
6. Mya perna : fhell oblong, dilated, the narrower bafe 
compreffed. It inhabits the Magellanic Straits, and the 
fnores of Barbary. It is faid to referable a ham, or leg of 
mutton ; it is fmooth, blue and white, and open at one 
end. 
7. Mya vulfella : fhell tongue-fhaped ; the hinge is ter¬ 
minal, depreffed, and femi-orbicular. The fhell of this 
lpecies varies in form according to its age. 
8. Mya arfilica : fhell ftriate ; the valves with two fub- 
fpinous ridges ; hinge without teeth. It is found in the 
North Seas among algae ; fize of a bean ; pale yellow, and 
milk-white within. 
9. Mya edentula : fhell oval, equivalve, wide, gaping^ 
and ftriate; hinge without teeth. It inhabits the fandy 
fhores of the Cafpian Sea, and is about an inch long. 
The fhell is thin, white, with about thirty-three ftriae in 
each valve. 
10. Myaradiata: fhell equivalve, pellucid, very finely 
ftriate tranfverfely, yellowilh-green with livid rays ; valves 
very broad on one lide and very narrow on the other. 
There is a variety which is brownifh, with blue radiate 
lines. It inhabits the rivers of Malabar. 
11. Mya oblonga: ovate-oblong; one valve with a 
broad flrong tooth let into a hollow of the other valve, 
and a fmaller tooth inferted between two frnall ones of the 
oppofite valve. 
12. Mya anatina : fhell globular, fnowy, pellucid; pri¬ 
mary tooth of the hinge prominent and rounded. It in¬ 
habits Guinea, and refembles the Solen anatinus. 
13. Mya Nicobarica : fhell equivalve, fnowy, ovate-ob¬ 
long, with decuffate flrise; tooth of the hinge fingle, 
broad, perpendicular, and fpoon-fhaped. It inhabits, as 
its name imports, the Nicobar-iflands. 
14. Mya auflralis: fhell ovate-compreftfed, clofed ; hinge 
with two lateral teeth. Found in New Zealand. 
15. Myagaditana: fhell rounded, flattifh, tranfverfely 
ftriate. It inhabits the fhores of Cadiz. 
16. Mya corrugata: fhell rhombic, green; the protu¬ 
berant parts wrinkled. It is found in the rivers of Coro¬ 
mandel, and is nearly an inch long. 
17. Mya rugofa: fhell oval, wrinkled, outwardly green- 
ifli, within pearly; primary tooth of the hinge crenulate, 
with a longitudinal lateral one, double in the other valve. 
It inhabits the rivers on the coaft of Coromandel. 
18. Myanodofa: fhell oval, thin, greenifh; the protu¬ 
berant parts knotty. 
19. Mya Norwegica: fhell oval, longitudinally and 
thickly ftriate; One end rounded, the other truncate; 
the protuberant parts are decorticated. 
20. Mya fpuria : fhell rhombic, green ; the protube¬ 
rant part glabrous. It is found in the rivers of Tranque- 
bar, and refembles the M. corrugata in every thing but 
its fize, being twice as large. 
21. Mya glycerneris: fhell gaping at both ends, very 
thick, lamelious, oblong-oval, with tranfverfe wrinkled 
ft rise; primary tooth in the hinge very thick. Inhabits 
the European Oceans, particularly the Spanifh and Me¬ 
diterranean Seas. It is five inches long and ten broad; 
and refembles a Solen. 
22. Mya fyrmatophora; fhell ovate, depreffed ; margin 
of 
