34 



CONCHOLOGY. 



ends; tlieliuigehns a tooth {hnped like an awl, bent back, 

 often double, and not inlerted, into the oppoiite (hell : 

 the rim at the fides appears fomewhat worn away, and 

 lias a horny cartilaginous articulation. Three of them, 

 the liliqua, vagina, and crifpus, are found among the fand 

 on the Britidi coalt, and generally in an ereft or perpen- 

 dicular dirciStion. Tlie filh has two pipes, each compofed 

 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 Itreaks or rays. Of 

 this genus there are twenty-three fpecies, the moft prized 

 of wliich is the radiatus. This (liell is of a light violet 

 ground, with filvery white rays, diverging from the hinge 

 to each extremity, fomewhat refembling the fun when 

 .ftiining through the clouds, and, what is vulgarly called, 

 drawing water. This knife-handle is very rare, and found 

 only ill the Indian ocean. 



PiNNA, or Se A-wi NO. — The pinnas, fea- wings or hams, 

 are fliells of a fomewhat triangular ihape, widening from 

 a pointed or narrow top to. a very broad end, which broad 

 end is always open. The hinge is inra'ticulatp, or hinge 

 without a tooth. The animal this fliell indoles is a kind 

 of Aug-. The fliell is fragile, and furnilhed with a beard. 

 Thefe are fo'jnd on fome parts of the coalts of Fr.ince, 

 Italy, and the Indian ocean. The largell and moft re- 

 markable are found in the Mediterranean. The animal 

 is blind, as are all of the genus ; which confifts of eighteen 

 ipecies. It is furniflied 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 moft prizeci 

 by conchologifts are the pinna muricata, rotundata, and 

 iiobilis. 



OF MUiriFALVES, OR SHELLS OF MANY PARTS. 



The third general divifion of teftaceous animals is into 

 nuiltivalvts, or thoie Ihells that are made up of many 

 diltinit pieces. There are three families in this divifion, 

 viz. I. Pholas, the piddock. 2. Lepas, the barnacle and 

 acorn fliell. 3. Chiton, the ofcabrion. 



PHOLAS, the piddcck.— Thefe fliells are trivalves, 

 ^laving two large valves, with a imall valve placed be- 

 tween them, near to the hinge. The hinge turns up on 

 the outer pait of the ihell, and under it, within the Ihell, 

 is a long curved tooth or Ipur. The word pbolas is de- 

 rived from the Greek, and fignifies fomething which lies 

 hid. This name they dtnve 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 luppofe, is, that they muft have 

 penetrated thefe fubllances when very fmall ; becaufe the 

 entrance of the hole in which the pholas lodges, is always 

 much lefs than the interior part of it, and, indeed, than 

 the fliell itfelf. Hence Ibme have fuppofed that they were 

 hatched in holes accidentally formed in ftoneSj and that 

 they naturally grew of ftich a ihape as was necefiary to fill 

 up the cavity. 



I he 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 fon:ewhat oblique to the horizon. The 

 openings of thele holes aie what betray the pholas being 

 in the (tone; but they are always very fmall in propor- 

 tion to the fize of the thell. There feems to be no pro- 

 grelhve motion of any animal in nature lb flow as that of 

 the phol.-\s ; it is immerfed in the hole, and has no move- 

 ment, except a linall one downwards, and this is only pro- 

 portioned to the growth of the animal. Its work is very 

 difiicult in its motion j but it has great time to peitorm 

 it in, as it only finks itfelf deeper in the ftone as it in- 

 creafes in btilk. That part by means of which it performs 

 this operation, is a flelhy iiibftance placed at the lower 

 extremity ol the Ihell 5 it is oi the fti-ipe of two points or 



claws turned towards eacli other, and is confiderably large 

 in proportion to the fize of the auiiual ; and though it be 

 of a loft fubltance, it is not to be wondered that in fo lonsT 

 a time it is able, by conftant work, to burrow into a hard 

 ftone. The manner of their performing this may be icen 

 by taking one of them out of the ftone, and placing it 

 U])on Ibnie 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 tlienilelves 

 in the mud in as large a hole as they had taken many 

 years to make in the ftone. They find little refiftance iii 

 fo foft a fubltance; and the iieceifity they feel for hiding 

 themfelves evidently makes them haiien tiieir work. The 

 body of the animal is lodged in the lower half of the hole 

 in the ftone, and the upper half is occupied by a trunk of 

 a flefliy fubltance and conical figure ; this they ufually 

 extend to the orifice of the hole, which doles or cruftj 

 over, lb as to leave the point or top of this inttrument 

 naked or bare. This trunk, though it appears fingle, 

 is, in reality, compoled of two tubes, or at leaft it is com- 

 pofed of two p.irts fepar.ated by a membrane. The arti, 

 fice of this double inftrument is fimilar to that in many 

 other (hell-fifli, namely, to take in lea-water by one tube, 

 and, when digelted, to rejeft it by the other. This trun^ 

 cated fleiliy inftrument is ukially about five inches long, 

 and from the firailaiity of its appearance, has acquired 

 to this fifli the trivial name of the J'ea-peiiis. In the mid- 

 dle of their bodies they have a fmall green veficle, the ufe 

 of which has not yet been difcovered. Thi.s, when plunged 

 ill fpirit of wine,'' becomes ot a purple colour : but its co- 

 lour on linen will not become purple in the fun like thas 

 of the murex ; and even if it would, its quantity is toO' 

 Jinall to make it worth preferving. 



The pholas fliell, as well as the included animal, is re- 

 markable for its luminous quality. That the fifli 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 of clothes, it makes them luminous. He alfo 

 fays that the light depends upon its moifture. The light 

 of this filh has furniflied natter for various obfei vations 

 and experiments to M. Reaumur and the Bolognian aca- 

 demicians, efpecially Beccarius, who took fo much pains 

 with the fubjeft of phofphoreal light. M. Reaumur ob- 

 ferves, that whereas other fiflies give light when they 

 tend to putrefcence, this is more luminous in proportion 

 to its being freih ; that when they are dried, their light 

 will revive if they be inoiftened either with freih or liilt 

 water, but that brandy iiiiniediately extinguiflies 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 fubject by M. F. Marfilius, in 1724, who 

 brought a number of thefe fliell-fiflies, and the ftones in 

 which they were inclofed, to Bologna, on purpofe for 

 their examination. Beccarius obleived, that though this 

 fifli ceafed to fliiiie vi'hen it became putrid, yet that in its 

 moft putrid ftate it would (hine, and make the water in 

 which it was immerfed luminous, when it was agitated. 

 Galeatius and Montius found that wine or vintgar ex- 

 tinguiflied this light ; that in common oil it continued 

 fome days ; but, in reiSified fpirit of wine or urine, it ex- 

 ifted hardly a minute. In order to obferve in what man- 

 ner this light was aftefted by different degrees of heat, 

 they made ufe of a Reaumur's thermometer, and found 

 that water rendered luminous by thefe fiflies increafed in 

 light till the heat arrived to forty-five degrees; but that 

 it then became fuddenly extinel, and could not be re- 

 vived again. In thele experiments of Beccarius, a folu- 

 tion of li;a-falt increafed the light of the luminous water ; 

 a folution of nitre did not incrcafeit quite fo much. Sal- 

 ammoniac diminilhed it a little, oil ot tartar/fr detiquiuni 

 nearly extinguiflied it, and the acids entirely. This water 

 poured upon frefli calcined gypfuiii, rock cryftal, ctrufe, 

 or fugar, became more luminous. Hi alio tried tlie ef- 

 feils of it when poured upon various other fubttances ; 



but 



