28 
MOLLUSGA. 
branchiae, but a mere net-work of pulmonary vessels which creep 
over the parietes of the resihratory cavity and chiefly on its ceiling-. 
Some of them are terrestrial ; others are aquatic, but are com- 
pelled to visit the surface from time to time for the purpose of open- 
Genus Aplysia 
.... Dolabella 
Sixth Family. 
Les Aplysiens. 
Respiratory organs situated as 
in the Bulli^ens, and also 
covered hy a shield ; hut this 
family possesses tentacula:. 
Second Section. — Les Pneumohranchiec. 
Genus Onchidium 
.... Parmacella 
.... Limax . . 
.... Testacellus 
.... Vitrina . . 
Seventh Family. 
Les Limacieiis. 
Genus Helix.... 
Carocolla 
Anostoma 
Helicina . . 
Pupa .... 
Clausilia. . 
Bulimus . . 
Achatina. . 
Suceinea. . 
Auricula . . 
Cyclostoma 
pBranchise, or respiratory organs 
' rampant, in the form of vas- 
cular net, on the thickness of 
a particular cavity, the aper- 
ture of which the animal con- 
tracts or dilates at will. 
L They only breathe fresh air. 
Third Order. — Les Trcichelipodes. 
Tlie bodies of the animals spirally contorted at their posterior part, which is sepa- 
rated from the foot, and always enveloped in a shell ; the foot free, flattened, 
attached to the lower base of the neck or at the anterior part of the body, and useful 
to assist the animal in crawling : a spiral shell covering the body. 
First Section. — Les Phytiphages. 
Animals feeding on vegetable substances. 
"Trachelipodes without a pro- 
jecting syphon, breathing 
generally by a hole. The 
greater number feed on vege- 
table substances, and are 
furnished with jaws : aper- 
ture of the shells entire, not 
having at the base any dorsal 
notch, or canal; they only 
breathe air. Shell spirivalve, 
smooth or with striae, the 
right margin often reflected 
outwardly ; smooth and not 
distinctly nacreous. This 
family is terrestrial ; they 
have cylindrical tentaculae, 
with eyes at their summits 
with or without an opercu- 
lum. They all live out of the 
- water. 
I ~ Amphibious Trachelipodes, with 
■ two tentaculae without eyes 
at their summit ; generally 
no operculum, their tentaculae 
flattened ; they inhabit fresh 
J water, and rise to breathe the 
' air on its surface. — Shell spi- 
rivalve, most frequently 
smooth on its external sur- 
face, and having the right 
margin of its aperture always 
sharp, and not reflected. 
With fourtenta- 
> culae. 
, With two tenta- 
culac. 
Planorbis 
Physa . . . , 
Lyranaea . , 
Second Family. 
Les Lymncens. 
L 
