39 ^ 
Terms em- 
ployed in 
defrribing 
Shells. 
CONCH 
beaks, and extends to one-third of the whole circum- 
ference of the valves. 
Margin pofterior (margo pofterior), extends to one- 
' third of the circumference from the beaks of the 
valves behind. 
— fuperior (margo fuperior), includes the upper 
part of the circumference of the valves comprehend- 
ed between the fuperior extremity of the. anterior 
margin, and the fuperior extremity of the pofterior 
margin. Hence the whole circumference of the 
(hell is divided into three equal parts. 
Margins of the valves (margines valvularum'l, fignify 
the whole interior circumference of the valves, in- 
cluding about the breadth of a line of the outer 
edge. They are divided into 
furrowed (margines canaliculati), having on 
fome part of the anterior circumference, afmall gut- 
ter parallel to it. 
notched (margines crenulati), furnifhed inte- 
riorly with rounded notches. 
— toothed (margines dentati), provided with 
pointed teeth. 
folded (margines plicati), furnifhed with folds 
which reciprocally correfpond with thofe of the op- 
polite valve. 
iimple (margines fimplices) having neither 
folds, teeth, nor notches. 
ftriated (margines ftriati), having longitudinal 
ftriae. 
Hinge. The hinge of a lhell is the moll folid and thick- 
eft part of the circumference of the valves, confti- 
tuting their bafe. It is almoft always furnifhed with 
teeth of different proportions, which ferve to fix the 
valves together. The hinge is 
- — compreffed (cardo depreffus), formed of one 
compreffed tooth. 
lateral (cardo lateralis), when it is placed at 
one of the fides of the fhell. 
oblong (cardo oblongus), when it occupies 
the whole bafe of the fhell. 
reflected (cardo reflexus), when its edges are 
folded back externally towards the convexity of the 
valves. 
terminal (cardo terminalis), fituated at the 
inferior extremity of the fhell. 
truncated (cardo truncatus), when the bafe 
of the fhell terminates tranfverfely and fuddenly, and 
the teeth of the hinge are fixed in this part. 
Teeth (dentes), are folid protuberances, commonly 
pointed, with which the hinge of fhells is ufually 
furnifhed, and which are deftined to fix the two 
valves together. They are divided into 
alternate (dentes alternati), when they are 
placed in a line parallel to the edges of the hinge ; 
and when the teeth of one valve are received into 
the interftices of the teeth of the other valve. 
— articulated (dens infertus), when it is receiv- 
ed in a correfponding cavity at the oppofite 
valve. 
forked (dens duplicatus feu bifidus), having 
the point divided into two. 
cardinal (dens primariusfeu cardinalis), is the 
tooth which is placed immediately oppofite. 
compreffed (dens depreffus), which is very 
much flattened, 
O L O G Y. _ Chap. III. 
Teeth ered (dens eredus), when the valve is laid on Terms em- 
the convex fide, the tooth rifes perpendicularly. ployed in 
longitudinal (dens longitudinals), when it ex- ^heiiT”' 
tends like a rib on the bafe of the valves. 1 ^ . 
Ihe dij~k (difeus), fignifies the convex centre of the 
valves, which is ufually fituated between the belly 
of the-fhell and its limb. 
Limb (limbus), is the circumference of the valves from 
the difk to their edges. 
Belly of the fhell (teftae umbo), is the moft inflated 
part of the valves. 
It is vaulted (umbo fornieatus) when in the interior of 
the valves it exhibits a cavity feparated from the 
hinge by a vertical membrane. 
Nates are two protuberances of a conical figure, 
fomewhat ipiral, which accompany the external bafe 
of moft bivalve fhells. They are 
— flattened (nates depreffse), when the furface 
is fenfibly compreffed. 
— approximate (nates approximatae), meeting to- 
gether when the fhell is fhut. 
horned (nates corniformes), when the angles 
being confiderable, and their diredion waved or fpi- 
ral, they refemble a horn. 
■ bent (nates incurvatae), when the curvature of 
the one is direded towards that of the other. 
feparated (nates diftantes), when' they are 
feparated from each other, at leaft the diftance of 
a line. 
diftant (nates remotiflimas), when the interval 
is very great. 
■ refleded (nates recurvse), when the curva- 
ture is direded towards the pofterior furface of the 
fhell . 
- — wrinkled (nates rugofae), when the furface is 
marked with unequal lines. 
fpiral (nates fpirales), when the curvature ex- 
hibits more than one circumvolution. 
Vulva, is fituated at the lorver part of the anterior mar- 
gin of the valves. It is divided into 
— — — hollowed (excifa, feu canaliculata), when it 
is marked with a groove during its whole length. 
— diftind (diftinda), marked by a perceptible 
difference of colour. 
— ■ lettered (feripta feu literata), when the fur- 
face is marked with lines refembling written cha- 
raders. 
— infleded (inflexa), when the edge of the lips 
is bent towards the inner furface of the valves. 
Anus, is an impreflion ufually hollow, placed at 
the lower part of the pofterior furface. It is divid- 
ed into 
— — bordered (marginatus), when it is circum- 
feribed by a diftind elevation. 
— beart-fhaped (cordatus), exhibiting the form 
of a heart. 
toothed (dentatus), furnifhed with teeth or 
notches. 
— lanceolated (lanceolatus), when the length is 
greater than the breadth, and the extremities are 
pointed. 
. — open (patulus feu hians), forming by the fe= 
paration of its edges, a confiderable opening, which 
penetrates into the interior of the fhell. 
—— — — oval (ovatus), of an elliptical figure. 
Valves-) 
