1 84 THE GASTROPODA 



The Pulmonata are divided into two sub-orders, Basommatophora 

 and Stylommatophora ; the former are generally aquatic, the latter 

 terrestrial. 



SUB-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, I). 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 Siphonaria. 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. 



FAMILY 1. AURICULIDAE, 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, Ferussac ; foot 



FIG. 173. ^ not divided transversely, but bifid 



otina otis, left-side view. co q , shell ; oc, posteriorly ; tentacles tapering ; shell 

 eye ; p, foot. solid, umbilical ed, 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 bind behind ; shell 

 solid, with a short spire and a narrow aperture. Carychium, 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. Blauneria, Shuttle- 

 worth ; shell sinistral ; aperture elongated, with a single columellar 

 fold. Pedipes, Adanson ; foot divided transversely ; shell globular ; th( 

 two borders of the aperture dentate ; partitions not absorbed. FAMILY 2. 

 OTINIDAE, Chenu. Shell with a short spire and a wide oval aperture ; 

 tentacles short. Genera Otina, Gray ; shell auriform ; marine ; British 

 (Fig. 173). Camptonyx, Benson; shell conical with a spiral summit; 

 terrestrial. FAMILY 3. AMPHIBOLIDAE, Adams. Visceral mass and shell 

 spirally coiled ; head broad, without prominent tentacles ; foot short, 

 operculated. Marine. Genus Am.phibola, Schumacher; from New 

 Zealand. FAMILY 4. SIPHONARIIDAE, Adams. Visceral mass and shell 



