CONCH 
and equally narrow mouth lengthways, which runs into a 
ftiort gutter at the top. Molt authors have added ano¬ 
ther character, that is, of always being thorny or fpiked, 
bumped, orotherwife rough all over the furface, like the 
(pikes or afperities of rugged rocks, from which it ob¬ 
tained the Latin name of murex, the Englifh one of rocks, 
and the French name of rockers-, but this character does 
not hold throughout the genus. 
The murices are divided into four genera, viz. i. Mu¬ 
rex, or rock-lhells, whofe mouth is oblong, narrow, and 
ends in a gutter at the top ; the clavicle or turban being 
generally (hort or nearly flat, and the pillar wrinkled or 
plaited. They are molt commonly very thick (hells, and 
extremely rugged on the outfide, from being wrought 
with bumps, prongs, foliations, and other fimilar works. 
This genus is very numerous, and fome of the fpecies 
are vaftly large and heavy. 
2. Rhombi, or (hells whofe fubordinate character is to 
have always a rhombic (hape or contour, fronvwhich par¬ 
ticular alone, as it carries an idea of the fubjeCts pro- 
poled, they have the name of rhombi. In the elder au¬ 
thors we find (hells called rhombi, but which appears to 
be a mere name without meaning or application. Thus 
Columna makes rhombus, turbo, (trombus, and trochus, 
all fynonymous. Lifter calls the volutes and olives, 
rhombi, or ftrombi; and Sibbald, Woodward, See. do the 
fame; but in the- modern authors, we feldom fee the 
name of rhombus ufed. This confulion apparently arifes 
from the double meaning of the Latin word rhombus, 
which not only iignifies a lozenge or rhombic figure, but 
alfo a reel, a fpinning-wheel, a whirl, or other rolling in- 
Itrument; and it is from this laft fimilitude "the olives 
and fuch like (hells have been called rhombi, by the elder 
authors, and not from a lozenge or rhombic figure, as 
fome have erroneoufly imagined. This genus is not fo 
numerous as the preceding, but contains many beautiful 
(hells ; and (ome very large and heavy. There is an ele¬ 
gant foffil fpecies of rhombus, not yet difeovered in a 
living (bite, found in France, and'in Hordell cliffs near 
Chriltchurch, in H amp (hi re. It is curioully figured in 
Brander-s Foftilia Hantonienfia, 
The third genus is the alatse, or winged rocks; fo named 
by moll authors from their lip being greatly extended, or 
expanded outwards, like-a flap or wing. Some few kinds 
have the wing quite fimple, or with the edges even ; but 
the greater part of thefe, as alfo of the aporrliais, have 
alfo near the top of the mouth a broad hollowed finus, 
called the /coop, from which appendage Lifter names them 
purpura feu buccina biliriguia. Rumphius and Meulchen 
make a diftinft genus of them, which they call alatae. 
Davila ranks thefe by themfelves in the third genus of 
hjs murices, by the name of fimple winged (hells; and 
Linnaeus ranks all the winged (hells together in his genus 
(trombus. This genus is very numerous, and contains 
many beautiful and coftly (hells. An elegant and large 
foftil kind of this (hell, not yet difeovered" living,, is alfo 
found in Hordell cliffs in Hampftnre, and figured in Bran- 
der’s Foftilia Hantonienfia. 
The fourth genus of murices is the aporrhais, or fpider- 
(hells, whofe edges are fet with ftrong and large prongs 
or fingers; hence they are called fpider-fhells, devil’s- 
claws, &c." Davila makes thefe his fourth genus of mu¬ 
rices, which he calls winged murices with prongs or fin¬ 
gers ; but all the other authors have intermixed them 
with the alatae. The fpecies are few, but they are elegant 
(hells.—-See fpecimens of them in the annexed copper¬ 
plates. A fpecies of murex has been found on the coafts 
of Guayaquil and Guatimala in South America, which is* 
laid to produce a purple colour fuperior to the famed Ty¬ 
rian dye. The abbe Raynal fays of it, that no colour yet 
known can be compared with this, either as to luftre, live- 
linefs, or duration. The progrefs of modern chemiftry, 
however, in the art of dying, has fuperceded all thel'e 
far-fetched encomiums. Thefe terminate ail the families 
and genera of univalve (hells. They are certainly the 
Vol. V. No. 251. 
O L O G Y. 29 
mod numerous of the teftaceous animals, and greatly ex¬ 
ceed the two general divifions of bivalves and multivalves 
joined together. In this aflemblage of univalves the ftu- 
pendous works of the creation are Angularly manitelted, 
by the immenfity of beauties in their colours and ltruc- 
tures. On this account it is that univalves are in general 
the choiceft objects of collectors, and bear more value 
than bivalves or multivalves. 
Of BIVALVES, or DOUBLE SHELLS. 
Thefe are compofed of two pieces, or parts, which, by 
means of a connexion by hinges, play on each other, fo as 
to open or (hut, and perform all other functions necefl'ary to 
the economy or way of life of the animal included in them. 
In relation to the fifties which inhabit them, they are de- 
feribed under their generic names, from the fyftem of 
Linnceus; it being the bufinefs of conchology to defenbe 
the (hells, and not the animals, or any of their parts. 
This divifion of bivalves may be arranged under three 
general heads, viz. (hells that have unequal valves, and 
(hut dole; as the efcallops, oyfters, anomite, See. (hells 
that have equal valves and (hut clofe ; as the cockles, tel¬ 
lens, rnufcles, Sec. and (helis with valves that never jhwt 
clofe, but are always open or gaping in fome part; as the 
tridac'nse, bafon-fliells, or bears paws, the chamse, pinna:, 
folenes, Sec. Under thefe three arrangements all the'bi- 
valves yet known may be ranked. Thefe three arrange¬ 
ments are alfo general ones; blit the chief or eflential 
character of bivalves is their cardo, or hinge; and there¬ 
fore by that charafter alone the families are diftinguifhed. 
Lifter begins his hillory of (hells with the bivalves, 
which he divides into two parts, and into twelve fami¬ 
lies. In his arrangement he has great regard to the cha¬ 
racter of the hinge, though lie does not entirely build 
upon it. His method, however, wants correction in his 
third family, or margaritiferse; in his feventh family, his 
placing the Noah’s arks or boats, as rnufcles; in his ninth 
family of tellens, which is not truly defined; and, lafily, 
in his making two families of the chama and chama pho- 
las, which in reality have no pofitive character to diitin- 
guifii them. Dr. Grew, in his Mufeum Regalis Societatis, 
gives, as his feventh (cheme of (hells, that of the bivalves 
and multivalves; but it is fo confuted as to be ufelefs as 
a fyftematic work ; however, his two chief divifions of 
bivalves are into inarticulate, and articulate, hinges. 
Breynius’s fcheme of bivalves is very jejune and ufelefs. 
Argenviile divides all his bivalves into fix families, viz. 
oyfters 5 chamae; rnufcles, tellens, and pinnse^ cordi*. 
formes, or cockles; elcallops; and lolens. This author’s 
method is entirely arbitrary ; nor does he characterize a 
lingle family by the cardo or hinge. 
Gualtieri forms his method from thole whofe valves 
and fides are equal or fimilar, which is his firft clafs; his 
lecond clafs confilts of thofe whole valves are equal, and 
their (ides unequal or diflimilar ; and his third clafs is of 
(hells with unequal valves. By this arrangement he re¬ 
jects the hinges as characters, and mixes all the families 
together, iolely on account of their fimilar or diflimilar 
fides; fo that it is impoflible to collate his method in 
fucli a manner as to be of much utility to the learner of 
conchology. The method of Mr. Tournefort divides all 
bivalves into two parts : firft, fuch as (hut clofe all round ; 
and, fecorid, fuch as are always open or gaping in (bine 
part. This divifion, though good, is incomplete, and his 
families and genera are very arbitrary. Linnaeus, in de- 
feribing the included animals or fi(h, divides all bivalves 
into fourteen genera, which he charafterifes- by their 
hinges in a very accurate manner; and his method feems 
to be the molt perfeft of any yet publi(hed. His arrange¬ 
ment is as follows: Mya, the pearl-oyfter; folen, the 
knife-handle; teilina, the teilen ; cardium, the cockle; 
maCtra, the pellucid oyfter; donax, truncated or flat- 
fided cockle 5 Venus, or concha-venerea, .gaping (hells, 
fo named from their refe mb lance to the pudenda of wo¬ 
men; i’pondylusj the thorny oyfter ; chama, (hells ofI the 
I cockle 
