262 PNEUMONOBRANCHIATA. 



11.; Jeffreys, Linn. Trans, xvi. 388. ; Turton, 

 Man. ed. 1. 11. f. 95. 



Helix nautileus. Walker, T. M. R. f. 20, 21. ; Mont. 

 p. 464. t. 25. f. 5. 



Turbo nautileus. Linn. S. Nat. i. 1241. ; Turt. 

 ZHcf. p.227. 



Var. 1. Shell smaller, with the transverse la- 

 minae more remote. 



Planorbis cristatus. Drap. p. 44. t. 2. f. 1 3. 



Var. 2. With the transverse laminae obliterated. 



Monstrosity, with the volutions detached and raised 

 above each other. 



In ponds and ditches, on aquatic plants. 



Animal grey. 



Shell the tenth of an inch in diameter, of a blackish 

 or greenish horn-colour, with three volutions; the 

 epidermis raised into numerous transverse ridges, 

 which form a spinous crest round the outer margin ; 

 aperture roundish-oval, united all round, and often 

 detached from the second volution at its narrower end. 



* * Spire flat ; whorls fiat above, keeled. 



104. 5. PLANORBIS carinatus. Carinated Coil Shell, 

 (t. 8. f. 89.) Shell horn- colour, transparent, 

 striate, nearly flat above, rather convex, and with 

 a slight central umbilicus beneath ; whorls six, 

 rapidly enlarging, with a prominent obtuse keel 

 in the middle ; mouth angular. 

 Planorbis carinatus. Mutter, Verm. ii. 157. ; 

 Drap. p. 46. t. 2. f. 13, 14. 16.; Brard, p. 150. 

 t. 6. f. 3.; Turton, Man. ed. 1. t. 16. f. 89. (not 

 87.). 

 Helix planata. Linn. Trans, viii. p. 189. t. 5. f. 14. 



