S2 



C O N C H O L O G Y. 



to the efpecial ufe of opening the tliells. It confilh or a 

 griiily or bony thin Itring, whicli twilts in and out to 

 above h.ilf-ivay within the fliells, )ike the twillings of 

 ribbantis, vulgarly called true lovers kmts. This is tlie 

 fecond fort mentioned by Davila. The other ftniiilurc, 

 •which is Davila's third fort, is a guttered triangular ap- 

 pendage, with a cut cr vent half-way down it, fixed per- 

 penditiilariy on the upper valve, from the top or beak, to 1 

 the middle of the fhell. 



A very furprifmg and unaccountable circumftance, re- 

 lative to the fofii! and recent teftaceous animals, already 

 noted, is, that all thofe found in iniiiienfe quantities in 

 the foflll Itate, are hardly known recent ; and 'vtce verfa. 

 This is inftanced in the ammonia, which are found in 

 incredible quantities fodil all over the world, though 

 none are yet dilcovtred recent or living; and this family 

 of anomia, though alfo found foflil in an allonilhing 

 abundance, has very few living fpecies yet diicovered. 

 See the article Anomia, vol. i. p. 741. 



Da Co(h* divides this family of aiiomiae into two ge- 

 nera, viz. I. Inarticulate anomiac, or thofe in which the 

 liinge of the under valve is of a large finus or cavity, the 

 eorners whereof form two prominencies or joints; and 

 the upper valve is indented into it by a corre<pondent 

 prominency to the cavity, and by two fmall hollows, 

 anfwerable to the two prominencies or joints. 2. Mult- 

 articulate anomia;, or thofe whofe hinge lies on a long 

 Itraiglit line, and is fet with many teeth, exadUy like 

 the Noah's aiks. — See figures of this divifion of bivalves, 

 in the annexed engravings. 



BIVALVES WITH EQUAL VALVES. 

 The'e confift of (hells that have equal fides, and (hut 

 clofe ; fuch as the cockles, teliens, nuilcles, &c. Thefe 

 again admit of three divifions, viz. i. Multarticulate, or 

 with a great number of teeth or articulations on the 

 binges. 2. Articulate, or with few teeth ; and, 3. Inar- 

 ticulate, or without any teeth. The multarticulate (hells 

 are called leptopolyginglymi, and 'confift of the three fol- 

 lowing families. 



PECTINOID^.— Thefe are fliells with equal valves, 

 generally very flat; the hinge lies on a (fraight line like 

 the efcailop, but is let with feveral parallel and ttraight 

 ridges and intermediate furrows, and the fides are difli- 

 milar. There are but few fpecies of them. Lifter ranks 

 the two kinds he figures by the name of peclines marga- 

 ritifcias polyginglymi. Woodward, among his peclunculi 

 leptopolyginglymi figura oblonga. Gualtieri figurts a kind, 

 and calls it concha longa brachiata ; and Seba figures 

 f^me among the pinnae, and calls them volfella : but they 

 are not methodized in any other writer on conchology. 

 There is a very large and extremely thick fpecies of this 

 family not yet known in a living (late, found foflil at 

 Eononia in Italy, which is fully del'cribed and figured in 

 the memoirs of the Bononian Inltlfute. 



FECrUNCULI POLYGINGLYMI.— The fliells of 

 this family refemble the cockle in all refpeifs except the 

 hinge ; which in thefe is multarticulate, or furnirtied with 

 a great number of teeth, but in the cockles there are only 

 a few. The rank theie (hells hold in Lifter, is peftuncuU 

 leptopolyginglymi margine rotunda. Woodward places 

 them in his clafs 3, on account of their being of a round- 

 irti fliape, (figura fubrolunJa.) Linnaeus ranks them 

 among his arcs; and the other authors have mixed them 

 iudikriminately with the common articulate cockles. 



AKCA. — This family contains Linnasus's genera of 

 arks 01 boats, which are fuch fliells as have their hinges 

 on a perfect Itraight line, and are of a fomewhat fquarifli 

 figure, or oblong ; as the Noah's aik, fquare cockle. Sec. 

 Lifter puts forae of this kind among the multarticuhate 

 cockles- ; and the Noah's arks he places among the muf- 

 cles, by the name of many-toothed mufcles. Woodward 

 ranks them among his polyginglymi forma, oblonga. Ar- 

 geuville places them in his fourth family of heart-fliaped 

 cocklejj but Davila makes them a diltintf genus of his 



fourth family, and calls them atks. Gualtieri forms a 

 genus of them by the name of concha rhomboi'dalis ; and 

 Meulchen alio ranks them as a dillinft genus of arks. 

 Dr. Ginelin enumerates forty-three fpecies, fome of which 

 are very curious and valuable (hells. To this family of 

 arks Da Cofta imagines the foflil hippocephaloidas be- 

 longs, and that they aie a fpecies of it yet undilcovered 

 ving from the (ea: his reafon for ranking them with the 

 at ks, and not the cunei, is, that they appear to be multar- 

 ticulate fliells. 



COCKLE — The elTential charafler of thefe fliells is, 

 a curved or (emilunar hinge, fet with from two to four 

 ftrong teeth. This family is fo extremely numerous, and 

 has befides fuch ftriking or remarkable lubordinate cha- 

 raflers, that it is with great propriety divided into three 

 genera, viz. i. The cardiimi, or common cockle. i.The 

 peiSlunculus, or Venus-(hell. 3. The donax, or truncated 

 cockle. Thele are as follow -. 



CARDIUM. — The common cockle. This genus is 

 every where known, and efteemed as food, being found 

 on the loofe iiindy coalh of molt countries. The fliells 

 are equally railed, dentated, and concave, and Ibme are 

 extremely haudfome. Dr. Gmelin, in his new edition of 

 the Syftema N iturse, defcribes fixty-feven I'pecies. 



VENUS. — Concha veneris, peftunculus, cordiform~ 

 cockle, or Vcnus-fliell ; fo called, from, the Angular con- 

 formation of its aperture, and refemblance of the fexual 

 parts of females. The fliells are moftly of a cordiform or 

 oblong fliape, and with fimilar and diflimilar fides, whofe- 

 beaks are not very peaked or prominent. Lifter inter- 

 mixes them with the two following genera, all by the 

 name of peftiinculi, and he has alfo placed feveral among, 

 his teliens. Argenville, Davila, and Meufchen, call them 

 canies ; and Davila divides them into four genera. Of 

 this genus there are one hundred and fifty-four Ipecies, 

 Ibme of which, as the Venus, Dione, &c. are very curious 

 and valuable (hells, 



DONAX. — The truncati, or flat-fidcd cockles. Thefe 

 are fuch as are tiuncated, or have one fide flat, and, as- 

 it were, cut off. Thefe (hells rank in raoft authors with 

 the cockles in general. Davila and Linn-ceus only, have 

 made a diftiniil genus of them. There are, according t<J 

 Gmelin, nineteen (pecies. 



TELLENS. — The teliinre, or teliens, are fliells more 

 broad than long, rather flat, and the hinge has two teeth 

 let clofe together. This family is divided into two ge- 

 nera, viz. i. TelliuES with fimilar fides, whofe beak and 

 hinge are central. 2. Cunei, or wedge-fliaped fliells, hav- 

 ing diflimilar or unequal fides, whole beak and hinge are 

 placed near to, or quite at one end : but thefe genera are 

 by mcjit authors promifcuoufly mingled togetlier. Lifter 

 places them after the pinna;; and defines them to be fliells 

 fhapcd like weilges. Woodward makes a genus of them, 

 and fays thty have few teeth on the hinge, and are ob- 

 long (hells, or with lengthened fides. Rumphius, Gual- 

 tieri, Linnxus, and Meufchen, have all a genus they call 

 tellina; Davila alfo, but he defines them very inaccurate- 

 ly, and includes the folens as a fpecies of them. Argen- 

 ville ranks them among the muicles. There are feveral 

 kinds of foflil cunei, which remain yet undifcovered in a 

 recent or living ftate ; Hud fome are very elegant and cu- 

 rious, particularly the ftudded kind. There are ninety 

 fpecies of them defcribed by Gmelin, 



MACTRA.— The placenta, or palhicid oyfter. Thefe 

 are (hells with equal valves, whofe hinge or cardo lies, 

 quite within the iliell, and on one valve tonfifts two ftraif 

 linear ridges, pretty prominent, and laid obliquely to 

 each other, I'o as to meet at one end in a very acute an- 

 gle; and the other valve has tv^o correfpondent iurrows. 

 There are twenty-feven fpecies now known, one of which 

 is found in the river Tees, in England. The next in 

 order are thofe bivalves that are inarticulate, or have no. 

 teeth on their hinge ; as the m.irgarititer;e, mufcles, &c. 



MYA, the PEAR.L OvsTER. — The niargaritifera', or 



pearl oyfters, are eared fiw:lls with equal valves, and tbeir 



a. hing* 



