THE GASTROPODA 187 
mantle produced anteriorly into a cervical lobe ; foot with a posterior 
dorsal mucous pore. Orpiella, Gray; differs from Ariophanta in 
having a horn-shaped protuberance at the hinder extremity of the foot. 
Vitrina, Draparnaud ; the mantle projects in front and on the right 
side, and partially overlaps the thin and depressed shell ; foot elongated, 
without a posterior mucous pore ; British. Helicarion, Férussac ; differs 
from Vitrina in having the foot truncated anteriorly, with a posterior 
mucous pore. Faminy 3. Limactpak, Gray. Shell almost completely 
covered by the mantle, or internal. Parmacella, Cuvier ; shell unguiform 
with a spiral summit ; the mantle occupies the centre of the body and 
completely covers the shell except for a very small orifice above the spire. 
Limav, Linnaeus ; shell wholly internal, without a spiral summit ; 
mantle reduced, and situated on the anterior part of the body ; 
pulmonary aperture towards the hind end of the pallial border ; British. 
Urocyclus, Gray ; shell oval, without a spire, internal except for a small 
median orifice in the hinder part of the mantle; pulmonary aperture 
in the middle of the pallial border; African. Parmarion, Fischer. 
Amalia, Heynemann. Agriolimaz, Mirch. Mesolimar, Pollonera. Mono- 
chroma, Simroth. Paralimax, Bottger. Metalimax, Simroth. Famity 4. 
PHItomycipAk, Fischer. No shell; the mantle covers the whole surface 
of the body ; radula with squarish teeth. Genus—Philomycus, Férussac ; 
foot broad; genital orifice near the right tentacle. Famity 5. 
OsTRACOLETHIDAE, Simroth. Shell largely chitinous, not spiral, its 
calcareous summit projecting through a small hole in the mantle which 
elsewhere covers it. Genus—Ostracolethe, Simroth. Faminy 6. ARIONIDAE, 
Gray. Shell internal or- absent; animal limaciform ; mantle restricted 
to the anterior and middle part of the body; radula with squarish 
teeth. Genera—Arion, Férussac ; respiratory orifice at the anterior end 
of the pallial border ; genital orifice close to the respiratory orifice ; shell 
reduced to simple isolated calcareous granules; British (Fig. 172, D). 
Geomalacus, Allinann ; shell internal, oval; Ireland.  Aviolimax, Mérch. 
Anadenus, Moreh. Faminy 7. 
HELIcIpAE, Gray. Shell with 
medium spire, external or par- 
tially covered by the mantle ; 
mandible folded ; radula with 
square teeth ; genital orifice below 
the right posterior tentacle ; geni- 
tal apparatus generally provided 
with a dart-sac and multifid 
vesicles. Genera — Helix, Lin- Fic. 177. 
naeus ; shell globular, conical or Helix, nemoralis, right-side view. I, anus; II, 
depressed, with a rounded or ex- ute! (ermaphrodite) pore; IID anterior ten: 
panded aperture (Figs. Ws A pneumostome in its maximum distension. 
and 177); British. (A large 
number of sub-genera has been established, which includes more than 
4000 species: Polygyra, Say. Sagda, Beck. Plewrodonta, Fischer von 
Waldheim. Helicodonta, Férussac. Helicophanta, Beck. Acavus, Mont- 
fort. Sitala, Adams. Chlorites, Beck. Hapalus, Albers, etc.) Bulimus, 
