270 RISSOID AS. 
subeffuse at the base, angulate above; peristome continuous, 
thickened, duplicate. 
PROSOSTHENIA ,Neumayr. Shell small, ovate-conical or turreted, 
longitudinally plicate ; last whorl coarctate, deflected ; aperture 
ovate, oblique, entire ; peristome continuous, thickened, dupli- 
cate, outer lip protracted. Tertiary; Austria. P. Schwarzt, 
Neum. (1xxiii, 77). 
FossARULUS, Neumayr. Shell small, subglobose, rimate, with 
revolving nodulous ribs, and longitudinal riblets; aperture 
widely ovate, effuse above and below; peristome continuous, 
thickened, duplicate. Tertiary; Austria. P. Stachei, Neum. 
(Ixxili, 78). 
Amnicona, Gould and Haldeman. 
Distr.—United States throughout, including California. A. 
limosa, Say (1xxiii, 79). 
Shell small, turbinately globose, thin, smooth, perforate or 
umbilicate ; aperture broadly ovate, not oblique, outer lip thin 
and sharp, not projecting anteriorly. Operculum corneous. 
Foot rather short and broad, expanded and broadly rounded 
behind ; rostrum short; tentacles cylindrical, blunt at their tips. 
Ova a-capsules semilenticular, with a laminiform limb, each con- 
taining a single ege. 
Toxosoma, Conrad. 
Disir.—Tertiary ; So. America. 7’. eborea, Conr. (Ixxiii, 1). 
Shell conical, polished, the aperture projecting, subovate, 
direct; peristome continuous. Columella concave, with a 
plait or tooth ‘in the middle, not oblique; base rounded, subum- 
bilicated. Mr. Conrad supposed this to be a land-shell; its 
position in the system cannot be accurately defined. 
Liosoma, Conrad. 
Distr.—Tertiary ; So. America. JZ. curta, Conr. (1xxiii, 2). 
Conical, polished ; aperture subelliptical; columella with one 
plait in the middle; base entire. Position very doubtful. 
SupraMity LITHOGLYPHINA. 
Shell small, globose, spire short, last whorl proportionally very 
large; lip sharp. Fresh water. 
Litnoaiypuus, Muhlfeldt. 
Disir.—Fresh water, So. E. Europe, So. America. JZ. lapi- 
dum, d’Orb. (1xxiii, 80, 81). 
Shell globular, thick, smooth, imperforate; spire short; suture 
not impressed ; aperture broadly subovate or nearly circular, 
inner lip callous, outer lip simple. Operculum corneous, 
rounded. 
