C 0 N C H O L O G Y. 
'lunge is merely a gutter or flight furrow without a (ingle 
tooth. The fpecies of this family are, the mother of 
pearl (hells or pearl oyfters, the ('wallow, &c. Da Coda 
and Linnaeus make a diftindt genus ot them ; but Lifter 
calls them pearly efcallops. Rumphius, Davila, and 
Meufchen, rank them as common oyfters. Woodward 
forms a genus he calls 'margari-tiferse; and defines it as 
eared (hells with a fmooth hinge; and Gualtieri defines 
them by placing the pearl (hells in one genus, by the 
name of couchse insequilaterse; and the (wallow in ano¬ 
ther genus, he calls conclue aliformes. 
The m.ya margaritifera is the fiih that produces the 
Britifti pearls. It has a viry thick, coarfe, opaque (hell, 
often much decorticated, oblong, bending inward on one 
lide, or arcuated, black ori the outfide ; ufual breadth from 
five to fix inches; length two and a quarter. It inhabits 
l’everal of the principal rivers of Great Britain, and is 
noted for producing quantities of pearl. There have been 
regular fiftieries for the lake of this precious article ; and 
fixteen have been found within one fliell. They are the 
difeafe of the fifli, analogous to the (tone in the human 
body. On being fqueezed, they will ejedf'the pearl, and 
often caft it fpontaneoufly in the (and of the dream. The 
river Conway was noted for them in the days of Cambden. 
A notion alfo prevails, that fir Richard Wynne of Gwydir, 
chamberlain to Catharine queen to Charles II. prefented 
her majefty with a pearl (taken in this river) which is to 
this day honoured with a place in the regal crown. They 
are called by the Welfli cregin dilmv, or “ deluge (hells,” 
as if left there by the flood. The Irt in Cumberland was 
alfo produ&ive of them. The famous circumnavigator, 
fir John Hawkins, had a patent for fifning in that river. 
He had obferved pearls plentiful in the Straits of Magel¬ 
lan, and flattered himfelf with being enriched by procur¬ 
ing them within his own ifland. In the feventeenth cen¬ 
tury, feveral of great fize were got in the rivers of the 
counties of Tyrone and Donegal, in Ireland. One that 
■weighed thirty-fix carats was valued at forty pounds, but 
being foul, loft much of its worth. Other Angle pearls 
were fold for ten pounds each. One was fold to lady 
Glenlealy, who put it into a necklace, and refufed eighty 
pounds for it from the duchefs of Ormond. Suetonius 
reports, that Casfar was induced to undertake his Britifli 
expedition for the fake of our pearls; and that they wepe 
fo large, that it was neceffary to ufe the hand to try the 
weight of a (ingle one. Mr. Pennant imagines that Caefar 
only heard this by report; and that the cryftalline balls 
called mineral pearl, were miftaken for them. We believe 
that Cselar was difappointed of his hope: yet he carried 
home a buckler made with Britifli pearls, which he dedi¬ 
cated to, and hung up in, the temple of Venus Genetrix: 
a proper offering to the goddels of beauty, who lprang 
from the fea. This is (uppoled to have been rather a 
contrivance, to imprefs the minds of the Roman citizens 
with the importance of his conquefts in Britain. It may 
not be improper to mention, that notwithstanding the 
claflic authors honour our Britifh pearls with their no¬ 
tice, yet they report them to have been (mail and ill-co¬ 
loured, an imputation that in general they are (till liable 
to. Pliny fays, that a red (mail kind was found about 
the Thracian Bofphorus, in a fliell called mya ; but does 
not give it any mark to afcertain the (pecies. 
Linnaeus made a remarkable difcovery' relating to the 
generation of pearls in this (i(h. It will bear removal re¬ 
markably well ; and it is faid, that in fome places they 
form refervoirs for the purpofe of keeping it, and taking 
out the pearl, which, in a certain period of time, will be 
again renewed. From obl’ervations on the growth of their 
(hells, and the number of their annular laminae or fcales, 
it is fuppofed the fifli will attain a very great age ; fifty 
or fixty years are imagined to be a moderate computation. 
The difcovery turned on a method which Linnaeus found, 
of putting thefe (hell-fiflt into a (late of producing pearls 
at pleafure, though the final effect would not take place 
for feveral years. He (ays, that in five or fix years after 
Vol. V, No. 151. 
the operation, the pearl will have acquired the fize of a 
vetch. We are unacquainted with the means by which 
he accomplidled this extraordinary operation ; but it was 
probably publiflied at the time, and considered as im¬ 
portant, (nice it is certain that the author was rewarded 
with a munificent premium from the dates of Sweden on 
this account. It is faid that the method confided in in¬ 
juring the fliell externally by a perforation ; and it has 
been observed, that thefe concretions in ftiell-fifli are foundT 
on the infide, exadlly oppofite to perforations and inju¬ 
ries made from without, by lerpulae and other animals. 
Gmelin enumerates twenty-four (pecies of mya. 
MYT.ILUS, (lie Muscle. —This conftitutes the lad 
family of bivalves with equal valvfs; they are not eared ; 
are mod generally very convex, of a long and narrow (Lapp, 
and the hinge is a mete flight furrow without any tooth, 
and is fituated not at the top 1 of the (lie!!, but a little way 
down one of the Tides. All conchologifts agree in the 
claiTification of this family of (bells ; and Dr. Gmejin 
enumerates fifty-eight (pecies. Several of ,them are re¬ 
markable for the beauty of their internal (hell, and for 
the pearls which are fometimes found in them. 
The edulis, or eatable mufcle, is plentiful in England, 
the heft of which are thofe called hookers, found in im- 
menfe beds on the coaft of Cumberland. They are taken 
out of the fea, and placed in the river Were, within reach 
of the tide, where they grow very fat and delicious. This 
fpecies is alfo found in all the European and Indian Teas. 
The mod valuable of thefe (hells is the ?naterperldmm, or 
mother-of-pearl (hell, defcribed by Rumphius. It is nearly 
orbicular, compreffed, and flat, the bafe tranfverfe, and 
imbricated with dentated coa'ts. On the infide it is ex- 
quilitely poliflied, and of the whitenefs and water of pearl 
iMelf. It has alio the fame luftre on the outfide, after the 
external laminae have been taken off by aquafortis and 
the lapidary’s mill. 
BIVALVES with GAPING VALVES. 
Thefe are termed concha hiantes, or bivalves whole (hells 
never (lint quite dole, but are open or gaping in fome 
part. This family confifts of three genera, viz. 1. Cha¬ 
ins, the gapers or bafon-fliells. 2. Solens, the (heaths or 
knife-handles. 3. Pinnae, the fea-wings or hams. 
CHAMA.—The gaper, or bafon-fliell. Thefe are of 
equal valves and diflimilar (ides,.in hinge and appearance 
like the cordifortn cockles, but c 1 the longed fide, from 
the beak to near the extreme margin, the two (hells do 
not clofe, but leave an oval opening or gap, the lips 
whereof are very broad, and turn up on the edges. This 
hiatus, or gap, is ufed by the animal to put forth or pro¬ 
trude its tentaculas or feelers, in fearch of food ; and alfo 
to fallen itfelf upon any piece of rock or folid body, fo as 
to counteraft the impulle of the wavesr There are twenty- 
fix fpecies, fome of which are nearly in the (hape of efcal¬ 
lops, and immenfely large; others are of an oblong form, 
very thick and rotund, fo that, when opened, the (hells 
form large capacious bafons. Others referable the rocky 
murices, or thorny oyfters; only that the fpiracles or 
fangs 'are much harder, firmer, and of a done-lilte con¬ 
fidence. The cbama gigas, found in the leas of Afia, are 
more than four feet over, and weigh from three hundred 
and a half to fix or fever, hundred weight. Their capa¬ 
city renders them extremely valuable to the Afiatics, who 
ufe them as watering-troughs for their cattle; and they 
almoft fupply the place of tanks, on the (bores of thole 
dry and thirity regions. Thefe (hel,l-fi(h, when arrived at 
mature age, are capable of pinching oft’ a drip’s cable as 
large as a man’s arm. The chama trapezia is alfo a very 
large and curious fliell, of great weight, andeafily formed 
into capacious balons. The chama cor is a rare and cu¬ 
rious (hell; the beak is hooded, and curvated like the 
bill of a parrot. The lazarus is rocky and full of prickles ; 
the barbator is beautifully ftriated and fringed. 
SOLEN. the Knife-handle. —Thefe are alfo called 
(heaths and razor-handles. Thefe (hells are open at both 
K ends; 
