SHELL. 
Lima. An inequilateral-eared bivalve; 
the valves a little gaping on one side ; binge 
without teeth ; ligament external ; beaks 
separated. This genus is founded chiefly 
on the Ostrea lima of Linnaeus, now named 
by Bruguiere, Lima squamos. The separa- 
tion of these shells from the Pectens, on the 
idea of their forming a byssus, whilst the 
Pectens do not, requires, it should seem, a 
more accurate kilowledge of the habits of 
the animals which occupy the different 
Pectens. 
Pecten. This, contrary to Linnaeus, is 
adopted by Bruguiere as a genus distinct 
from Ostrea. Its characters are given : a 
regular bivalve shell ; the valves unequal ; 
the hinge without teeth, most commonly 
eared, with a triangular pit for the ligament. 
The hinge shutting by a black lipment 
fixed in this triangular pit, and the different 
forms of the shells are the circumstances 
which are supposed to warraiit the proposed 
separation. 
Pedum. The shell from which this genus 
has been formed, and of which only one 
species is known, being that which is figured 
by Chemnitz and Favanne, is semi-trans- 
parent, unequal valved, eared ; the inferior 
valve gaping; the beaks separated; hinge 
without teeth; ligament external, and at- 
tached to a long and narrow gutter. The 
upper valve is striated, and granulated lon- 
gitudinally ; but the under valve is smooth, 
sharply edged, and hollowed out in one 
part. 
Perna. An irregular, flatfish, bivalve, 
shell: the hinge composed of many linear, 
parallel teeth, disposed in a straight line, 
across. The hinge is closed by a ligament 
which is attached between the teeth, and 
which, by its thickness, prevents the teeth 
from articidating witli each other. Ostrea 
perna, isogona, ephippium, pictum, and 
legumen, of Linnmus, aie placed under this 
genus. I 
Avicula. This genus Lamarck forms from 
Mytilus hirundo, Linnaeus, which is the only 
shell in the genus. He describes it : an 
irregular, loose shell; a little gaping towards 
its beaks, and having the valves of unequal 
size. The hinge callous, without teeth ; a 
little oblong pit, which i% marginal and 
parallel with the edge which supports the 
ligament. 
Malleus. The hammer-oyster of Linnaeus, 
with two other species, form this genus, 
according to Lamarck, who gives fur the 
characters of the genus: an irregular loose 
shell, a little gaping near its beaks, having 
equal valves ; a callous hinge, without 
teeth, having a conical pit, placed obliquely 
on the edge of each valve. This genus 
seems to be hardly sufficiently distinguish- 
able from the last ; nor does the name of 
the genus appear to be well adapted, since 
some of the species no ways resemble a 
hammer in their form. 
Vulsella. This genus is formed from the 
Mya vulsella of Linnaeus. The uncertainty 
with which this shell has been viewed, at 
different periods, shows the uncertainty of 
its nature, and the propriety of not placing 
it under any other genus. Linnaeus had 
once considered it as a Pinna, and Bruguiere 
as an oyster. It is a loose shell, longitudi- 
nal, and nearly equivalved, terminating in 
a very short bent beak ; the hinge callous, 
depressed, and without teeth, of equal ele- 
vation on each valve, forming a rounded 
conical pit for the ligament. 
Ostrea. In this genus is comprehended 
those shells only which are oysters, accord- 
ing to common acceptation. The charac- 
ters of the genus are, therefore, an irregu- 
lar, adherent, inequivalve shell ; the hinge 
without teeth ; an oblong pit, sulcated 
across, giving attachment to a ligament. 
Gryphaea. The shell, for the reception 
of which this genus was established by 
Lamarck, was improperly considered as a 
species of Anomia by Linnaeus, and as a 
species of oyster by Bruguiere ; to which 
latter genus it undoubtedly very nearly 
approximates. It is a loose unequivalved 
shell ; the inferior valve concave, terminat- 
ed by a beak turned upwards, and bent 
into an involved spire; the superior valve 
smaller, like an operculum ; the hinge with- 
out teeth; but with an oblong and dented 
pit ; and one muscular impression in each 
valve. Lamarck enumerates eight fossil 
species of this genus. 
Plicatula is a genus formed, by Lamarck, 
from Spondylus plicatus of Linnaeus. It is 
an angulated shell, with unequal valves and 
unequal beaks, which are pointed ; the edges 
are in deep plaits ; its hinge is formed of 
two strong teeth on each valve, and an in- 
termediate pit for the reception of the liga- 
ment; with one muscular impression on 
each valve. 
Spondylus. In this genus of Linnaeus are 
comprised bivalve, irregularly-formed shells, 
the hinge of which is formed of two strong 
hooked teeth, and an intermediate pit for 
the ligament ; in the inferior valve are two 
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