184 THE GASTROPODA 
The Pulmonata are divided into two sub-orders, Basommatophora 
and Stylommatophora ; the former are generally aquatic, the latter 
terrestrial. 
Sus-ORDER 1. BASOMMATOPHORA. 
Testaceous Pulmonata with an external shell. The head bears a 
single pair of well-developed contractile but not invaginable tentacles, at 
the bases of which are the eyes (Fig. 107, 1). The stomach, or at least a 
part of it, is very muscular. The penis is at some distance from the 
female aperture, except in Amphibola and Stphonaria. All have an 
osphradium (except the Auriculidae, which are terrestrial), which is 
situated outside the pallial cavity in those forms in which water is not 
admitted into the lung (Limnaea, Planorbis, Fig. 89, etc.). There is a 
veliger stage in the development, but the velum is reduced. 
Famity 1. Auricunmag, Blainville. Terrestrial and usually mari- 
time animals ; the genital duct monaulic, the penis being connected with 
the hermaphrodite opening by an open or closed groove (Fig. 171); shell 
with a prominent spire, the internal 
partitions often absorbed and the aper- 
ture denticulated. Genera—Auricula, 
Lamarck ; foot not divided ; tentacles 
swollen at their extremities; shell 
thick, oval, with an elongated aper- 
ture, and two folds on the columellar 
border.  Cassidula, Férussac ; foot 
Fic. 173. not divided transversely, but bifid 
Otina otis, left-side view. cog, shell; oc, posteriorly 5 tentacles tapering ; shell 
eye; p, foot. solid, umbilicated, with a short spire. 
Alexia, Leach ; tentacles swollen and 
pigmented at their extremities; shell thin with a pointed spire, the 
exterior border of the aperture slightly thickened; British (Fig. 67). 
Melampus, Montfort ; foot divided transversely and bifid behind ; shell 
solid, with a short spire and a narrow aperture. Carychiwm, Miiller ; 
tentacles thick and short, with the eyes on the inside ; shell small and 
short ; the aperture oval with a denticulated internal border ; terrestrial ; 
British. Scarabus, Montfort ; foot not divided ; tentacles tapering ; shell 
oval with a pointed spire, and a very constricted aperture, the margins 
bearing alternate teeth. Leuconia, Gray ; foot divided ; tentacles short 
and compressed ; shell thin, oval, with a conical spire ; aperture oval, 
the columellar border with a single fold; British. Blawneria, Shuttle- 
worth ; shell sinistral; aperture elongated, with a single columellar 
fold. Pedipes, Adanson ; foot divided transversely ; shell globular ; the 
two borders of the aperture dentate ; partitions not absorbed. Famrty 2. 
Ormnipak, Chenu. Shell with a short spire and a wide oval aperture ; 
tentacles short. Genera—Otina, Gray ; shell auriform ; marine ; British 
(Fig. 173). Camptonyxz, Benson; shell conical with a spiral summit ; 
terrestrial. F Amity 3. AMPHIBOLIDAE, Adams. Visceral mass and shell 
spirally coiled ; head broad, without prominent tentacles; foot short, 
operculated. Marine. Genus—Amphibola, Schumacher; from New 
Zealand, Famity 4. SIPHONARIIDAE, Adams. Visceral mass and shell 
