TESTACEOUS FISHES; 247 



moulded. If the animal has any tumour or excrefcence, it creates a fwel- 

 ling in that part of the incruftation to which it correfponds. When it 

 makes additions to its apartments, the fame protuberance which had 

 raifed the fhell before, fwells it again at fome little diftance, by which the 

 fame inequality runs fpirally all round the fhell. Sometimes thefe tu- 

 mours are fo large, or pointed, that their counterparts in the incruf- 

 tation appear like horns : thefe quitted, and others made, increafes their 

 number. If the body be channelled, the fhell that covers it will be 

 channelled likewife. Their diverfity is fo great, their figures and colours 

 fovery ftriking, that feveral perfons have made their arrangement the 

 bufinefs of their lives. Some fhells, fuch as the Stairs Shell, or the Ad- 

 miral Shell, are equally precious, by their fcarcenefs, as pearls. Shells 

 exhibit great difference of figure j fiat, concave, long, lunated, drawn 

 round in a circle, the orbit cut in two; fome rifing on the back, fome 

 fmooth, fome wrinkled, toothed, flreaked, the point variouQy intorted> 

 the mouth pointing like a dagger, folded back, bent inwards : all thefs 

 variations, and many more, furnifh at once novelty, elegance, and fpe- 

 culation. 



Ariftotle has divided them into three kinds : firft, the Univalve, or 

 Turbinated, which confift of one piece, like the box of afnail; fecond- 

 ly, the Bivalve, confiding of two pieces, united by a hinge, like an 

 oyflerj thirdly, the Multivalve, confiding of more than two pieces, as 

 the Acorn Shell, which has not lefs than twelve. Thofe fifhed up from 

 the deep, are called by the Latin name felagii ; thofe caft on (bore, arci 

 called littorales. Many of the pelagii are never feen on (here ; they 

 continue in their native depths, and we owe their capture to accident. 



Sea-fhells exceed both land and foffil fhells in beauty, in high polifh, 

 and in brilliant and various colouring. Frefh-waters have but two kinds 

 of fhells J the bivalved and the turbinated. Land fhells are but of one 

 kind, the turbinated; but in that are four or five very beautiful varie- 

 ties. Foflll, or extraneous fhells, are in great numbers, and of as many 

 kinds as in the fea itfelf, and which our mofl exa(5t and induflrious fhell- 

 coUeftors have not been able to fifh up from the deep, and probably 

 thoufands of different forms ftill remain at the bottom unknown. 



Tti OF 



