156 THE GASTROPODA 



with an aquiferous system ; propodium reflected over the head ; eyes 

 deeply seated or absent ; operculum spiral ; burrowing animals. Genera 

 Natica, Adanson ; shell globular, thick and polished, umbilicated, 

 with a semi-lunar aperture (Fig. 47) ; British. Amaura, Holier ; shell 

 not umbilicated, thin, with an oblong aperture. Siyaretus, Lamarck ; 

 shell auriform, with a very short spire and large aperture ; operculum 

 small and rostrate. FAMILY 41. LAMELLARIIDAE, d'Orbigny. Shell thin, 

 more or less covered by the mantle, and with a small spire ; no operculum 

 or propodium; mandibles fused dorsally. Genera Veluti?ia, Fleming; 

 shell only partially covered by mantle ; British. Lamellarw, Montagu ; 

 shell internal, spiral, transparent ; British. Marseniua, Gray ; shell not 

 completely covered by the mantle ; hermaphrodite. Oticidiop*M t Beck ; 



FIG. 134. 



Xenophonis exutus, animal and shell, left-side view, a, snout ; b t cephalic tentacles ; c, left 

 eye ; d, anterior part of the foot (to the ri^ht of this is seen the posterior lobe of the foot bear- 

 ing the sculptured operculum/). (From Uinkester, after Owen.) 



shell internal, membranous, without spiral ; hermaphrodite. FAMILY 

 42. TRICHOTROPIDAE, Gray. Shell with short spire, umbilicated, carinate 

 and pointed. Genus Trichotropis, Broderip and Sowerby. FAMILY 43. 

 SEGVENZIIDAE, Verrill. Shell trochiform, with canaliculated aperture 

 and twisted columella ; operculum spiral. Genus Seguenzia, Jeffreys ; 

 abyssal. FAMILY 44. JANTHINIDAE. Shell thin ; operculum absent ; 

 tentacles bifid ; eyes absent ; foot short, provided with an epipodium and 

 secretes a float ; radula with similar pointed teeth (Fig. 74, D) ; pelagic. 

 Genera Janthina, Lamarck ; shell blue, with a short spire ; ctenidium 

 with long pointed filaments, capable of being protruded from the pallial 

 cavity (Fig. 135). Recluzia, Petit; shell white with elongated spire. 

 FAMILY 45. CYPRAEIDAE, Fleming. Shell inrolled, solid, polished, the 

 spire nearly hidden, the aperture very narrow in the adult ; pallial 

 aperture provided with a short anterior siphon ; a short proboscis ; anus 

 posterior ; foot broad ; osph radium with three lobes ; mantle reflected 



