GASTEROPODA. 
Shell related to certain Valvate, with an infundib'iliform 
umbilicus ; no operculum. 
Distribution, .3 species. Lake Baikal, Siberia. 
PHYSELLA, Pfeiffer, 1861. 
Founded on P. Berendti, said to be a terrestrial shell from 
Mirador, Mexico. 
Shell like Bulla, spire minute; last whorl elongated; columella 
simple, arched, not truncated; peristome simple, straight. 
FAMILY Y.—AURICULIDA* 
Contains the following genera :— 
AvRiIcuLA, Lamarck. (See p. 304.) 
Sub-genera, Alexia (A. myosotis), Leach (p. 305); Leuconia 
(A. bidentata), Gray. 
PotyoponTA, Fischer (Pythia, Bolten) (p. 304). 
PEDIPES, Adams (p. 304). 
Distribution, 6 species. 
Sub-genus :—Marinula, King. M. pepita. The animal has 
not the transverse groove of the foot of Pedipes. 
Shell more elongated and destitute of spiral striz ; two con- 
vergent parietal plaits, columellar plait smaller, oblique; peri- 
stome rather simple. 
Distribution, 10 species. Madeira, South America, Australia, 
Philippines. 
MeEtAmpvus, Montfort (Ophicardelus, Beck; Tralia, Gray; 
Laimodonta, Nuttall; Pira, Tifata; Signia and Persa, Adams; 
Cremnobates, Sw.) (p. 304). 
Sub-genus, Oassidula, Ferussac (Lhodostoma, Sw. 3 ; Sidula, 
Gray). Aperture banded. 
PLECOTREMA, H. and A. Adams, 1853. 
Type, P. typica, Adams. 
Synonym, Lirator, Beck. 
Shell oyate-conic, or rather fusiform, solid, spirally grooved ; 
aperture oblong, contracted; columellar plait single, parietal 
plaits two, the lower of which is bifid; peristome thickened, 
sometimes terminating in a varix, bearing within two or rarely 
three teeth ; axis imperforated or umbilicated. 
* See p. 303. 
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