156 THE GASTROPODA 
with an aquiferous system; propodium reflected over the head; eyes 
deeply seated or absent ; operculum spiral ; burrowing animals. Genera 
—WNuatica, Adanson; shell globular, thick and polished, umbilicated, 
with a semi-lunar aperture (Fig. 47); British. Amaura, Moller ; shell 
not umbilicated, thin, with an oblong aperture. Szgaretus, Lamarck ; 
shell auriform, with a very short spire and large aperture ; operculum 
small and rostrate. Faminy 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—Velutina, Fleming ; 
shell only partially covered by mantle; British. Lamellaria, Montagu ; 
shell internal, spiral, transparent ; British. Marsenina, Gray ; shell not 
completely covered by the mantle ; hermaphrodite. Oneidiopsis, Beck ; 
Fig. 134. 
Xenophorus ecutus, animal and shell, left-side view. a, snout; b, cephalic tentacles ; c, left 
eye; d, anterior part of the foot (to the right of this is seen the posterior lobe of the foot bear- 
ing the sculptured operculum f). (From Lankester, after Owen.) 
shell internal, membranous, without spiral; hermaphrodite. FamiLy 
42. TRICHOTROPIDAE, Gray. Shell with short spire, umbilicated, carinate 
and pointed. Genus—Tvrichotropis, Broderip and Sowerby. Faminy 43. 
SEGVENZUDAE, Verrill. Shell trochiform, with canaliculated aperture 
and twisted columella ; operculum spiral. Genus—Seguenzia, Jettreys 
abyssal. Faminy 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. 
Faminy 45. CyprarIDAE, 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; osphradium with three lobes; mantle reflected 
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