VALVATA. PALUDINA. 47 



LES PERISTOMIENS. 



VALVATA. FLUVIATILE. 



Discoid or conoid; whorls cylindrical, umbilicated ; 

 margins united and acute; operculum orbi- 

 cular. 



V. pisciNALis. Globular-conoid^ somewhat 

 trochus-shaped^ deeply umbilicated ; apex obtuse^ 

 longitudinally wrinkled^ covered with a greenish 

 yellow epidermis. B. \. T, 114. 



V. spiRORBis. Slightly concave above^, and 

 umbilicated, so as to expose the interior volutions 

 beneath ; horn-colour, striate transversely, three 

 volutions. 1^. B. T. 115. 



PALUDINA. FLUVIATILE. 



Conoid; volutions rounded or convex ; aperture 

 sub-rotund, ovate or oblong, angulated above ; 

 margins of inner and outer lips united, with 

 edges acute, but not reflected; operculum horny, 

 orbicular. 



P. viviPARA. Thin, oval, acute ; whorls five, 

 much inflated, olive, with three brown bands ; 

 sutures deeply impressed, finely striate longi- 

 tudinally ; aperture pear-shaped, a little produced 

 at the upper angle ; inner lip a little reflected, so 

 as to close the umbilicus. 1^. B. T. 118. 

 P. ACHATiNA. Thin, conic -oval, acute; 



