TRACHELIPODA. 89 



obtruding above the plane of the opening ; destitute of an oper- 

 culum. 



Physafontinalis. — The Fountain Physa. — Plate XIII. fig. 

 6. Volutions reversed, oval, diaphanous, glossy, horn-colour- 

 ed ; spire short and acute. Half an inch long. Inhabits the 

 ditches and sti;eanns of Europe. 



Genus 68.— LUTE A.— Broww. 



Generic Character — Shell globidar ; spire short, subacute; 

 aperture ovate ; outer lip not continuous, slightly inflected at 

 top, and acute at the base ; a little reflected on the base of the 

 columella, and subumbilicated. 



Lutea lacuna. — The Lake Lutea. Plate XIII. fig. 10. 

 Very diaphanous, slightly wrinkled, and of a greenish horn-co- 

 lour. Half an inch long. Inhabits the ditches in Britain. 



Genus 69.— PL AN KB IS — Lamarck. 



Generic Character. — '^heW discoid; spire depressed; the 

 volutions apparent on both sides ; aperture oblong, luniform ; 

 <ixis of shell remote ; margin not reflected ; destitute of an 

 operculum. 



Planorhis carinatus. — The Keeled Planorbis. Plate XIII. 

 fig. 11. Depressed; upper side concave, with a keel round the 

 middle of the body. Three-fourths of an inch in diameter. In, 

 habits the ditches and lakes of Europe. 



GenuslO — PL ANA RI A.— iirown. 



Generic Character. — Shell discoid, depressed on both sides ; 

 the volutions conspicuous on either side ; spire lightly produced 

 above, and concave beneath ; aperture ovate ; edges of outer lip 

 acute ; destitute of an operculum. 



Planaria alha.—Tn^ White Planaria. Plate XIII. fig. 

 17. White, slightly wrinkled transversely ; outer lip with a nar- 

 row margin behind. One-fourth of an inch in diameter. In- 

 habits the coast of Dunbar, — Scotland. 

 h3 



