PLANORBIS. PHYSA. LYMN^EA. 43 



neath, with a spinous ridge round the outer whorl; 

 aperture oval, united all round, thin, pellucid, 

 blackish or greenish horn-colour; diam. j. B. 

 T. 94. 



P. COMPLANATUS 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 tioisted; outer lip very thin, 

 acute, partly obtruding above the plane of the 

 opening, destitute of an operculum. 



P. FONTiNALis. Revcrscd, oval, diaphanous, 

 smooth, yellowish horn-colour ; spire very short, 

 somewhat acute. B. f. T. 110. 



P. HYPNORUM. Reversed, ovate - oblong, 

 smooth, diaphanous, shining, yellowish ; spire 

 exserted, very acute ; aperture narrow, oval, cover- 

 ing about half the shell; whorls scarcely raised. 

 B. 1. T. 113. 



LYMN/EA. 



Oblong, sometimes turreted ; spire exserted; ajjer- 

 ture entire, oblong; outer lip acute; lower part 



