CONCHOLOGY. 



iiuige IS merelj' a gutter or flight furrow without a fingle 

 tooth. The Ipecies of this family are, the mother of 

 pearl (hells or pearl oyfters, the fwallow, &c. Da Cofta 

 and Linna?js make a diftinft genus of them ; but Lifter 

 calls them pearly eCcallops. Rumphius, Davila, and 

 Meufchen, raivk them as common oyfters. Woodward 

 forms a genus he calls margaritifsrse; and defines it as 

 eared (hells with a fmooth Jiiiige j and Gualtieri defines 

 them by placing the pearl (hells in one genus, by the 

 name of conchs insequilaters j and the fwallow in ano- 

 ther genus, he calls conchae aliformes. 



The mya raargaritifera is the filh that produces the 

 Britilh pearls. It has a very thick, coarfe, opaque (hell, 

 often much decorticated, oblong, bending inward on one 

 fide, or arcuated, black on tlie outfide ; ufnal breadth fiom 

 five to fix inches ; length two and a quarter. It inhabits 

 feveral of the principal rivers of Great Britain, and is 

 noted for producing quantities of pearl. There have been 

 regular fi(heries for the lake of this precious article; and 

 (ixteen have been found within one (hell. They are the 

 difcale of the fifli, analogous to the (tone in the human 

 body. On being fqucezed, they will ejeft the pearl, and 

 often cad it fpontaneoully in the land of the liream. The 

 river Conway was noted for them in thedays of Cambden. 

 Anotion a!fo prevails, that fir Richard Wynne of Gwydir, 

 chamberlain to Catharine queen to Charles II. prefented 

 her niajefty with a pearl (taken in this river) which is to 

 this day honoured with a placein the regal crown. They 

 are called by the Welfli crcgin dilunv, or " deluge fliells," 

 as if left there by the flood. The Irt in Cumberland was 

 alfo prodoitive of them. The famous circumnavigator, 

 iir John Ha«kins, had a patent for filhing in that river. 

 He had obferved pearls plentiful in the Straits of Magel- 

 lan, and flattered himklf with being enriched by procur- 

 ing them within his own illand. 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 fingle pearls 

 vere fold for ten pounds each. One was fold to lady 

 Gienlealy, who put it into a necklace, and refufed eighty 

 pounds for it from the duchel's of Ormond. Suetonius 

 reports, that Casfar was induced to undertake his Britifh 

 expedition for the 1-ike of our pcarh ; and that they were 

 fo large, that it was nccellary to u(e the hand to try the 

 weight of a fingle one. Mr. Pennant imagines thatCa;lar 

 only heard this by report ; and ti.3t the cryllalline balls 

 called mineral pearl, were miftaken for them. We believe 

 that C3?Iar was difappointed of his hope: yet he carried 

 home a buckler made with Britiflr pearls, which he dedi- 

 cated to, and hung up in, the temple of Venus Genetrix : 

 a proper offering to the goddefs of beauty, who (prang 

 from the fea. This is fuppofed to have been rather a 

 contrivance, to imprel's the minds of the Roman citizens 

 wish the importance of his conquefts in Britain. It may 

 •not be inTj^roper to mention, that notwithftanding the 

 clafTiC authors honour our Britilh pearls with their no- 

 tice, yet they report them to have been (mall and ill-co- 

 loured, an imputation that in general they are (till liable 

 to. Pliny (;iys, that a retf (mall kind was found about 

 the Thracian Bofphorus, in a (hell called mya-y but does 

 not give it any mark to alcert.iin the ipecies. 



Linnaus made a remarkable difcovery relating to the 

 generation of pearls in this fidi. It will bear removal re- 

 markably wcil ; and it is faid, that in fome places they 

 form refervoirs for the piirpole of keeping it, and taking 

 out the pearl, which, in a certain period of time, will be 

 again renewed. From obfervations on the growth of their 

 (hells, and the number of their annular laminse or (calcs, 

 it is fuppofed the fi(h will attain a very great age ; fifty 

 or fixty years are imagined to be a moderate computation. 

 The difcovery turned on a method which Linnsus found, 

 of putting thefe (hell-filh into a l\ate of producing pearls 

 at pleafure, though the final e(fe<5t would not take place 

 for feveral years. He (ays, that in (ive or ixy, years after 



Vol. V. No, 151, 



the operation, the pearl will have acquired the fize of a 

 vetch. We are unacquainted with tiie means by which 

 he accomplillicd this extraordinary orfieration ; but it was 

 probably publiflied at the time, and confidered as im- 

 portant, fince it is certain that the author was rewarded 

 with a munificent premium from the ftates of Sweden on 

 this account. It is faid that the method confilled in in- 

 juring the (hell externally by a perforation ; and it has 

 been obferved, that thtle concretions in (liell-filh are found 

 on the infide, exactly oppofite to perforations and inju- 

 ries made from without, by ferpulK and other animals. 

 Gmelin enumerates twentv-four fpecies of mya. 



MYTILUS, the Muscle — ^This conftitutes the laft 

 family of bivalves with equal valves ; they are not eared ; 

 are mo(f generally very convex, of a long .^nd narrow (hape, 

 and the hinge is a mere (light furrow witliout any tooth, 

 and is fituated not at the top of the (hell, but a little way- 

 down one of the fides. All conchologifts agree in the 

 clafli/ication of this family of (hells ; and Dr. Gmelin 

 enumerates fifty-eight fpecies. Several of them are re- 

 markable for the beauty of their internal (lieil, and for 

 the pearls which are fometimes found in them. 



The edulis, or eatable mulcle, is plentiful in England, 

 the beft of which are thole 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 feas. 

 The moft valuable of thefe fl-.ells is Xht mater perlarutn, or 

 mother-of-pearl fhell, defcribed by Rumphius. It is nearly 

 orbicular, comprelTed, and fl^t, the bafe tranfverfe, and 

 imbricated with dentated coats. On the infide it is ex- 

 (juifitely poliflied, and of the wliitenels and water of pearl 

 itfclf. It has alfo the lame luftre on the outfide, after the 

 external laminae have been taken o(f by aquafortis and 

 the Lapidary's mill. 



BIVALVES WITH GAPING VALVES. 



Thefe are termed conchx hianfes, or bivalves whofe (hells 

 never (hut quite i.loie, but are open or gaping in (ome 

 part. This family confifts of three genera, viz. i. Cha- 

 mae, the gapers or bafon-(hells. i. Solens, the flieaths or 

 knife-handles. 3. Pinna:, the fea-wings or hams. 



CHAMA. — The gaper, or balbn-(hell. Thefe are of 

 equal valves and diHimilar fides, in hinge and appearance 

 like the cordiform cockles, but on the longeft fide, from 

 the beak to near the extreme mar;; in, 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 tentacuise or feelers, in (tjarch of food ; and alfo 

 to faften itfelf upon any piece of rock or (olid body, (b as 

 to counteraft the impuife of the waves. There are rwenly- 

 fix fpecies, fome of which are nearly in the (hape of efcai- 

 lops, and immenfeiy hrge; others are of an oblong form, 

 very thick and rotund, fo that, when opeMe<l, the (hells 

 form large capacious bafons. Others reiemhle the rocky 

 murices, or thorny oyfters ; only that the fpiracles or 

 fangs are much harder, finner, and of a (tone-like con- 

 filteiice. The chama gigas, found in the fe.as of Afia, are 

 more than four (ect over, and weigh from three hundred 

 and a half to i\-:i or feven hundred weight. Tlveir capa- 

 city renders them extremely valuable to the Afiatics, wha 

 ufe them as watering-troughs for their cattle; and they 

 almolt lupply the place of tanks, on the fhores of thole 

 dry and thirlty regions. Thele (hell-fifli, wlien arrived at 

 mature age, are capable of pinching off a (hip's cable as 

 large as a man's arm. The chama trapezia is alfo a verv 

 large and curious (hell, of great weight, and eaJily form.ed 

 into capacious batons. The chama. cor is a rare and cu- 

 rious (heli ; the beak is hooded, and curvated like the 

 bill of a parrot. The lazarus is rocky and full of prickles ; 

 the barbator is beautifully (friated and fringed. 



SOLEN, the Knife-handle. — Tbt(e are alfo called 



flieaths and razor-handles. Thele flielis a.re open at both 



K «r.d3: 



