32 •" CONCH 
to the efpecial ufe of opening the (hells. It confifts of a 
griftly or bony thin ft ring, which twills in ami out to 
above half-way within the (hells, like the twiftings of 
ribbands, vulgarly called true lovers knots. This is the 
fecond fort mentioned by Davila. The other llrudlure, 
which is Davila’s third fort, is a guttered triangular ap¬ 
pendage, with a cut or vent half-way down it, fixed per¬ 
pendicularly on the upper valve, from the.top or beak, to 
the middle of the (hell. 
A very furprifing and unaccountable circumftance, re-, 
lative to the foftil and recent teftaceous animals, already 
noted, is, that all thofe found in immenle quantities in 
the foftil (late, are hardly known recent; and vice verfn. 
This is inftanced in the ammonia, which are found in 
incredible quantities foftil all over the world, though 
none are yet difcovered recent or living; and this-family 
of anomia, though alfo found, .foftil in an aftonifhing 
abundance, has very few living fpecies yet difcovered. 
See the article Anomia, vol. i. p. 741. 
Da Cofta divides this family of anomise into two ge¬ 
nera, viz. 1. Inarticulate anomia;, or thofe in which the 
hinge of the under valve is of a,large iinus or cavity, the 
corners whereof form two prominencies or joints; and 
the upper valve is indented into it by a correl'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 
ftraight line, and is fet with many teeth, exaftly like 
the Noah’s arks.—See figures of this divifion of bivalves, 
in the annexed engravings. 
BIVALVES with EQUAL VALVES. 
Thefe cor.fift of (hells that have equal Tides, and (hut 
dole; fuch as the cockles, tellens, mufcles, &c. Thefe 
again admit of three divifions, viz. 1. Multarticulate, or 
with a great number of teeth or articulations on the 
hinges. 2. Articulate, or with few teeth ; and, 3. Inar¬ 
ticulate, or without any teeth. The multarticulate (hells 
are called leptopolyginglymi, and conlift of the three lol 5 - 
lowing families. 
PECTINOIDj®.—T hefe are (bells with eqdal valves, 
generally very flat; the hinge lies on a ftraight line like 
the efcallop, but is fet with feveral parallel and ftraight 
ridges and intermediate furrows, and the Tides are difli- 
milar. There are but few fpecies of them. Lifter ranks 
the two kinds he figures by the name of pedliiies marga- 
ritifeice polvginglymi. Woodward, among his peflunculi. 
leptopolyginglymi figura oblonga. Gualtieri figures a kind, 
and calls it concha lcnga brachiata; and Seha figures 
fome 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 Hate, found foftil at 
Bononia in Italy, which is fully defcribed and figured in 
the memoirs of the Bononian Inftitute. 
PECTUNCULI POLYGINGLYMI.—The (hells of 
this family referable the cockle in all refpedts except the 
hinge ; which in thefe is multarticulate, or furniftied with 
a great number of teeth, but in the cockles there are only 
a few. The rank thefe (hells hold in Lifter, is pebunculi 
leptopolyginglymi margine rotunda. Woodward places 
them in his clal's 3, on account of their being of a round- 
ilh (hape, (figura fiubrotunda.) Linnaeus ranks them 
among his arcs; and the other authors have mixed them 
indifcriminately with the common articulate cockles. 
ARCA.—This family contains Linnaeus's genera of 
arks or boats, which are fuch (hells as have their hinges 
on a perfect ftraight line, and are of a fomewhat fquarilh 
figure, or oblong; as the Noah’s ark, fquare cockle, &c. 
Lifter puts fome of this kind among the multarticulate 
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- 
genvflle places them in his fourth family of heart-ftiaped 
cockles; but Davila makes them a ailtinb genus of his 
O L O G Y. 
fourth family, and calls them arks. Gualtieri forms a 
genus of them by the name of concha rhomBoi'dalis ; and 
Meufchen alfo ranks them as a diftinb genus of arks. 
Dr. Gmelin enumerates forty-three fpecies, fome of which 
are very curious and valuable (hells. To this family of 
arks Da Cofta imagines the foftil hippocephaloidae be¬ 
longs, ami that they are a fpecies of it yet undiscovered 
living from the fea: his reafon for ranking them with the 
arks, and not the cunei, is, that they appear to be multar¬ 
ticulate (hells. 
COCKLE —The eflential charaber of thefe (hells is, 
a curved or lemilunar hinge, fet with from two to four 
itrong teeth. This family is fo extremely numerous, and 
has betides fuch linking or remarkable lubordinate cha¬ 
mbers, that it is with great propriety divided into three 
genera, viz. 1. The cardium, or common cockle. 2. The 
pebunculus, or Venus-fliell. 3. The donax, or truncated 
cockle. Thefe are as follow : 
CARDIUM.—The common cockle. This genus is 
every where known, and elleemed as food, being found 
on the loofe fandy coafts of moll countries. The (hells 
are equally raifed, dentated, and concave, and fome are 
extremely handfome. Dr. Gmelin, in bis new edition of 
the Syftema Naturae, defcribcs iixty-feven fpecies. 
VENUS. — Concha veneris, pebunculus, cordiform 
cockle, or Venus-ftiell; fo called, from the Angular con¬ 
formation of its aperture, and refemblance of the fexuul 
parts of females. The (hells are moftly of a cordiform or 
oblong (hape, and with fimilar and diflimilar (ides, whofe 
beaks are not very peaked or prominent. Lifter inter¬ 
mixes them with the two following genera, all by the 
name of pebunculi, and he has alfo placed feveral among 
his tellens. Argenville, Davila, and Meufchen, call them 
cames; and Davila divides them into four genera. Of 
this genus there are one hundred and fifty-four fpecies, 
fome of which, as the Venus, Dione, &c. are very curious 
and valuable (hells. 
DONAX.—The truncati, or flat-fided cockles. Thefe 
are fuch as are truncated, or have one fide flat, and, as 
it were, cut off. Thefe (hells rank in mod authors with 
the cockles in general. Davila and Linnseus only, have 
made a diftinb genus of them. There are, according to 
Gmelin, nineteen fpecies. 
TELLENS.—The tellinae, or tellens, are (hells more 
broad than long, rather flat, and the hingfe lias two teeth 
fet clofe together. This family is divided into two ge¬ 
nera, viz. 1. Tellinse with fimilar fides, whofe beak and 
hinge are central. 2. Cunei, or wedge-lhaped (hells, hav¬ 
ing diflimilar or unequal fides, whofe beak-and hinge are 
placed near to, or quite at one end : but thefe genera are 
by mod authors promifcuoufly mingled together. Lifter 
places them after the pinnae; and defines them to be (hells 
ftiaped like wedges. Woodward makes a genus of them, 
and fays they have few teeth on the hinge, and are ob¬ 
long (hells, or with lengthened fides. Rumphius, Gual¬ 
tieri, Linnaeus, 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- 
vilie ranks them among the mufcles. There are feveral 
kinds of foftil cunei, which remain yet undifcovered. in a 
recent or living (late ; and fome are very elegant and cu¬ 
rious, particularly the ftudded kind. There are ninety 
fpecies of them defcribed by Gmelin. 
MACTRA.—The placenta, or pellucid oyfter. Thefe 
are (hells with equal valves, whofe hinge or cardo lies 
quite within the (hell, and 011 one valve confifts two ftrait 
linear ridges, pretty prominent, and laid obliquely to 
each other, fo as to.meet at one end in a very acute an¬ 
gle; and the other valve has two correfpondent furrows. 
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 margaritifer»,-mufclesy See. 
MYA, the Pearl Oyster.— -The margaritifera?,- or 
pearl oyfters, are eared (hells with equal valves, and their 
1 hinge 
