SHELL. 
disposition which Linnscus adopted ; bnt 
this is certainly by no means the ne plus ul- 
tra : other divisions appear in some instances 
deserving of adoption, and new genera re- 
quire to be admitted. It is therefore in- 
tended to give here Liimmus’s arrangement 
of the genera, omitting the species; after- 
wards to give that which has been adopted 
by Du Bose, agreeable to tlie discoveries 
and observations of Lamarck, Bruguiere, 
and others ; and to otter a few explanatory 
remarks, for the purpose of showing the 
propriety or impropriety of the deviations 
from the arrangement of Linnaeus. 
JIULTIVALVE SHELLS. 
Genus^l. Cliiton. The animal covered 
by several shells lying on each other along 
the back. 
2. Lepas. The shell, which is formed of 
several unequal and erect valves, is aftixed 
by its base. 
3. Pholas. Shell bivalve and divarfeated, 
with smaller, accessory, ditferently formed 
pieces at the hinge. 
BIVALVES, OR CONCH.®. 
4. Mya. Gaper. Shell generally gaping 
at one end ; the hinge with, for the most 
part, a thick, solid spreading tooth, not in- 
serted in the opposite valve. 
5. Solen. Razor-shell. Shell oblong, 
gaping at both ends; hinge with a subulated 
reflexed tooth, often double, not inserted 
in the opposite valve: the lateral margin 
rather obsolete. 
6. Tellina. The foreside of the shell slop- 
ing downwards ; the hinge, in general, with 
three teeth ; the side teeth, in one of the 
valves, being either flat or wanting. 
7. Cardium. Shell with equal and nearly 
equilateral valves, longitudinally ribbed, or 
sulcated, the margin dentated ; the hinge 
having, in the middle, two alternating teeth, 
one commonly incurved, and two lateral 
remote teeth, inserted info each other. 
8. Mactra. Shell with equal, bnt inequi- 
lateral valves; the hinge a complicated, 
central tooth, with an adjoining pit, and re- 
mote lateral teeth, inserted iii the opposite 
valves. 
9. Donax. The anterior margin of the 
shell very obtuse, the margin often crenu- 
lated ; two teeth at the hinge, and on the 
hinder margin, a, single one (rarely two, or 
three, or none) somewhat remote. 
10. Venus. The lips lying over the an- 
terior margin ; the hinge with three teeth 
close together, the lateral ones diverging 
from the apex. 
11. Spondylus. With rigid, unequal 
valves ; the hinge being formed by two re- 
curved teeth, with a cavity beUyeen. 
12. Chama. The shell heavy ; the hinge 
a gibbous projection, inserted in an oblique 
cavity ; the fore pai'ts closed without carti- 
lages. 
13. Area. Equivalved ; the hinge with 
numerous, acute, and alternately inserted 
teeth. 
14. Ostrea. With unequal valves, some- 
times eared ; the hinge an ovate cavity, 
without teeth ; but, in general, with lateral, 
transverse stri® ; no space or depression at 
the ligament. 
15. Auomia. The valves unequal, one 
flattish, the other gibbous, and one of them 
often perforated at the base ; the hinge a li- 
near projection, with a lateral tooth, which, 
in the flat valve, is inserted in the margin ; 
two bony rays support the animal. 
16. Mytiliis. Shell coarse, generally af- 
fixed by its byssus ; hinge generally w'ith- 
oiit teeth, being distinguished by a linear, 
subulated, longitudinal furrow'. 
17. Pinna. A sub-bivalve, brittle, erect, 
and gaping, having a silky beard. The- 
hinge without teeth ; the valves adhere on 
one side. 
UNIVALVE SHELLS, OR COCHLEj®. 
18. Argonauta. Shell spiral, involute, 
membranaceous, and with one chamber. 
19. Nautilus. Divided into many cham- 
bers, by partitions, perforated with project- 
ing pipes. 
20 . Conus. Convoluted and turbinated 
shell; the aperture longitudinal, linear, 
open at both ends, and without teeth ; the 
base entire, and the columella smooth.' 
21. Cyprasa. Involuted, sub-ovate, ob- 
tuse, and smooth ; the opening longitudi- 
nal, linear, dentated on each side, and ex- 
tended to both ends of the shell. 
22. Bulla. Convoluted, without spire, 
opening longitudinal, oblong, and contract- 
ed at the ends, entire at the base ; the colu- 
mella oblique and smooth. 
23. Voluta. Unilocular and spiral; the 
aperture without a tail, and somewhat open 
at both ends; columella plaited, with no 
inner; or colnmellar lip, nor umbilicus. 
24. Buccinum. Spiral and gibbous ; the 
aperture oval, terminating in a gutter, 
Vfhich, with the cauda, runs out to the 
right ; the interior lip smooth. 
25. Strombus. Spiral, with one side 
large, the aperture frequently with a dilat- 
