PLANORBIS. PHYSA. LYMNAA. 43 
neath, with a spinous ridge round the outer whorl; 
aperture oval, united all round, thin, pellucid, 
blackish or greenish horn-colour; diam. }. B. 
£104. 
P. compLaANnatus of Turton. Glossy, trans- 
parent, striolate, concave above, with the outer 
volution very convex, and abruptly larger, and a 
strong, prominent, obtuse keel near the base, flat 
beneath; diam.}. B. T. 89. 
PHYSA. FLUVIATILE. 
Generally sinistral, convolute, oval or oblong; spire 
prominent ; aperture longitudinal, contracted 
above ; columella twisted ; outer lip very thin, 
acute, partly obtruding above the plane of the 
opening, destitute of an operculum. 
P. FoNTINALIS. Reversed, oval, diaphanous, 
smooth, yellowish horn-colour; spire very short, 
somewhat acute. B.?. T. 110. 
P. uyPpNnoruM. Reversed, ovate - oblong, 
smooth, diaphanous, shining, yellowish; spire 
exserted, very acute ; aperture narrow, oval, cover- 
ing about half the shell; whorls scarcely raised. 
Bee. 7 2118. 
LYMNAA. 
Oblong, sometimes turreted ; spire exserted ; aper- 
ture entire, oblong; outer lip acute ; lower part 
