102- PBOVISIONAL AID TO THE STUDY OF TASMANIAN MOLLITSCA. 



(lxv.) Family LiMN^iDiE. 

 Shell thin, horn-coloured, mostly spiral, sometimes patelli- 

 form, capable of containing the entire animal, con- 

 tracted ; aperture simple, rounded ; lip sharp. 



Genus Limh/ea. (530-533.) 

 Shell normally dextral, oval-oblong, thin, corneous, translucid ; 

 spire sharp, more or less acuminated ; last whorl 

 ventricose ; aperture oval, ample, rounded in front; 

 columella lip with an oblique plait entering above. 

 Dist. — Europe, Asia, America, North of the Equator, 

 Polynesia. 



Genus Amphipeplea. (534-535.) 

 Shell globular, ventricose, thin, transparent; spire very 

 short, depressed ; aperture very large ; columella 

 without fold ; outer lip sharp. Dist. — Europe, East 

 Indies, Australia, Philippines. 



Genus Physa. (536-547.) 

 Shell ovate, sinistrally spiral, thin, polished ; aperture 

 rounded in front. Dist. — ■North America, Europe, 

 East Indies. 



Genus Planorbis. (548-551.) 

 Shell discoidal, biconcave, the whorls visible on both sides ; 

 aperture small, rounded, margin usually simple, 

 sometimes expanded. Dist. — World-wide. 



Genus Ancylus. (552-554.) 

 Shell conical, limpet-shaped, thin ; apex posterior turned to 

 the left ; aperture with entire basal margin ; interior 

 with a sub-spiral muscular scar. Dist. — North and 

 South America, Europe, Australia. 



Genus Gundlachia. (555-556.) 

 Shell very small, thin, obliquely conic, apex inclined 

 posteriorly and to the right ; base two-thirds closed by 

 a flat, straight-edged shelf, leaving a semicircular 

 aperture. Dist. — United States, Cuba, Tasmania. 



(lxvi.) Family Amphibolid^e. 



Genus Amphibola. (557-559.) 



Shell sub-globose, rather thick, rugose, umbilicated ; spire 

 short, whorls shouldered above, umbilicated ; aperture 

 sub-oval ; columella lip callous ; columella flattened 

 and reflected; outer lip sinuous posteriorly; operculum 

 corneous, sub-spiral. Dist. — New Zealand. 



