SHELL. 
longer than wide. This shell had been 
placed by Linnaeus among the Helices, 
under the name of Helix halidtoidea ; and 
by Midler among the Bullae, under tlie name 
ofBulla velutina ; but Lamarck seems very 
properly to have disposed of it under a dis- 
tinct intermediate genus between the Ne- 
rites and the ear-shells. 
Stomatia. Is a genus which has been 
formed by Helblins and Lamarck from a 
shell, which had been placed under the ge- 
nus Haliotis, but which wanted the holes, 
which exist in the shells of that genus. 
Argonauta. A very thin, single chambered 
univalve shell j the spire concealed in the 
internal part of the shell. 
Concholepas. An oval univalve, convex 
in its superior part', with its summit ob- 
liquely inclined upon the left edge ; the ca- 
vity simple ; two teeth and a sinus at the 
base of the right edge. Dargenville and 
others had placed the shell of this genus 
among the Patellae ; but Bruguiere having 
seen several with tendinous opercula, dis- 
posed them under the genus Buccinum. 
Lamarck has however thought fit to consi- 
der it as forming a genus, connecting the 
Patellae with the other spire valved shells. 
Nerita. A semiglobular univalve, flattish 
beneath, not umbilicated at the spire ; the 
opening semicircular the columella or par- 
tition, nearly transverse. Lamarck has 
retained in this genus only the imperforated 
Nerites ; the others he transfers to the next 
genus. The Nerites have not only no um- 
bilicus but no true columella, having in its 
place, a simple partition ; which is flat, 
thin, and longitudinal, originating in the 
groove of the first spire, and generally 
dentated. 
Natica. This genus of Lamarck’s is cha- 
racterized by a nearly globular shell, umbi- 
licated at the left lip with a callosity at the 
umbilicus; the opening semicircular; the 
columella oblique, and not dentated. 
Helicina. This genus is founded by La- 
marck on a shell figured by Lister (Plate 
LXXI. fig. 59) and which he describes as a 
globular shell ; the opening entire, semioval ; 
columella with a callus, compressed infe- 
riorly ; an operculum. The propriety of 
this adoption cannot be judged of, from 
merely the figure of this shell in Lister’s 
work. 
Helix. An orbicular or elongated uni- 
valve, with an obtuse or concave spire; the 
opening Entire, forming a half moon. La- 
marck divides the shells which have been 
hitherto disposed under this genus into 
eight genera. 1. Bulimus, an oval or oblong 
shell, the opening whole, longer than wide ; 
the columella smooth, without folds, trun- 
catiire or widening at the base ; as in Bulima 
hsemastoma. 2. Lymnaea, an oblong sub- 
turriculated shell, longer than wide ; open- 
ing entire, the inferior part of the right 
edge, turning up and passing into the open- 
ing, and forming a very oblique fold on the 
columella ; as in Helix stagnalis. 3. Mela- 
nia, a turriculated shell ; the opening entire 
oval or oblong, widened at the base of the 
columella ; Helix amarnla is of this genus. 
4. Ampullaria, a globular bellied shell, um- 
bilicated at its base, no callosities on the 
left lip; the opening entire, longer than 
wide. Helix ampullacea forms this genus. 
.5. Planorbis. A discoid shell, the spire 
flattened or sunk, not prominent, the 
opening entire, longer than wide, and filled 
laterally by the convex projection of the 
last turn but one. The type of this genus Ls 
Helix planorbis. 6. Haliotidea. 7. lan- 
thina. 8. Helix, a globular shell, with a 
convex or conoidal spire ; and particularly 
with the opening diminished by the projec- 
tion of the last iturn but one; but as this 
last character is common to the Planorbis 
also, these two genera are evidently con- 
founded. The separation which is hereafter 
made of some shells which originally were 
in the genus Helix, in agreement with the 
ideas of Bruguiere, will be, therefore, more 
correct. 
Volvaria, a cylindrical shell, twisted on 
itself, without a projecting spire ; the open- 
ing narrow, as long as the shell ; one-or more 
folds on the base of the columella. This 
genus was formed by Lamarck from a shell 
which is figured and described by Pennant, 
vol. iv. Plate LXX. fig. 8.5. He considers it 
as intermediate between Bulla and Bulima. 
Bulla. A tumid shell, the spire not pro- 
jecting ; the opening as long as the shell ; no 
umbilicus. This genus of Linnaeus has been 
much reduced by Bruguiere, who placed 
several species under Bulima, and esta- 
blished his genus Ovula. Lamarck has still 
further reduced them, by forming the genera 
Terebellum, Pyrula, Ampulla, and Achatina. 
lanthina. This genus is formed by La- 
marck on a single shell described by Lister, 
Brown, Forskal, and other naturalists ; 
which derives its claims of distinction from 
Helix, not so much from the character of 
the shell as from that of the animal, which 
differs in its structure materially from the 
animal of the Helix, since it is furnished 
with a curious apparatus, being an inhabi- 
