LIMNiEID^. 103 



in one piece, arcuated, finely striated with a superior, central 

 fibrous projection, recalling the accessory plate in Succinea. 

 Radula composed of oblique teetli, the central multicuspid, the 

 laterals and marginals serrated and furnished with a small, nar- 

 row, special appendage at their superior, outer margin. 



PHYSELLA, Hald., 1842. Shell very small, globular, with short 

 and small spire ; aperture oval, ample ; columella with a well- 

 marked plication. F.globosa^ Hald. (ciii, 15^. 



PHYSODON, Hald., 1842. Shell oval-elliptic, rather solid; colu- 

 mella toothed. P. microdoma^ Hald. (ciii, 16). 



COSTATELLA. Dall. Shell longitudinally, laminately costate. 

 Ph. costata, Newc. (ciii, 17). 



Aplexa, Fleming, 1828. 



Syn. — Nauta, Leach, 1831. 



Distr. — 25 sp. Europe, North America, Northern Asia. Fossil. 

 Eocene of Europe and United States. A. hypnorum, L. (ciii, 19). 



Shell sinistral, thin, elongated, polished ; spire conical, acu- 

 minated, with scarcely indented sutures ; aperture narrowly 

 elongate-oval ; columella simple ; outer lip sharp. Animal with 

 plain mantle-margins. 



MACROPHYSA, Meek, MSS. Spire enormously elongated, body- 

 whorl and aperture small. B. columnaris, Desh. (ciii, 20.) Paris 

 Basin. 



BuLTNUS, Adanson, 1757. 



Syn. — Isidora, Ehrenberg, 1831. Diastropha, Gray, 1840. 



Distr. — Mediterranean region, W. Indies, Oceanica. 



Shell like Physa, oval, with very convex whorls and deep 

 sutures, apex obtuse ; an umbilical slit ; columella twisted ; peris- 

 tome simple. 



Animal resembling Aplexa ; jaw in three plates ; radula with 

 bicuspid central, tricuspid laterals, serrated marginals. 



Physopsis, Krauss, 1848. 



Distr. — Africa. P. Africana., Krauss (ciii, 21). 



Shell like Physa, but columella truncate below. 



platyphysa, Fischer, 1883. Last whorl enlarged at the 

 shoulder; columella truncate below. P. Prinsepi, Sowerby. 

 Eocene ; India. 



PYRGOPHYSA, Crossc, 1879. Spire turreted. Africa, Mada- 

 gascar. Probably passes into Isidora, Ehrenb. P. Wahlbergi^ 

 Krauss. Africa. 



AMERTA, H. Adams, 1861. (Gl^qDtophysa, Crosse, 1870.) Shell 

 spirally sculptured, the body-whorl sometimes smooth, not 

 glossy. 2 sp. New Caledonia, Australia. P. lirata^ Trist. 

 (ciii,'l8). 



