26 COLIMACEA. 



white curved, remote, equidistant lines, radiating from the um- 

 biHcus ; these are the internal septa which divide the chambers ; 

 under side nearly flat, and umbilicated ; aperture oval, and 

 somewhat triangular ; outer lip interrupted. Diameter not a 

 quarter of an inch. 



Found in stagnant water, adhering to aquatic plants. 



This shell may be easily confounded with the Planorhis 

 niticlus, but if inspected through a lens the concamerations will 

 be at once perceived. 



Family IV.— COLIMACEA. 



Spiral ; destitute of any exterior projections, except the 

 additions of growth ; outer lip frequently reflected ; terrestrial 

 or amphibious ; tentacles of the animal cylindrical, with or 

 without an operculum. 



Section I. — Animals with two tentacles. 



Genus X.—CYCLOSTOMA.— Lamarck. 



Shell turbinated, variable in shape, thin ; the apex in most 

 species obtuse, and the volutions ventricose ; aperture entire, 

 circular, or nearly so in the adult state ; outer lip more or less 

 angular at the upper part, sometimes thickened, usually reflected 

 and united all round, and frequently externally fringed ; oper- 

 culum spiral, horny, but inclining to testaceous in some species, 

 consisting of a few depressed convolutions, provided with a sim- 

 ple testaceous internal coating. 



L Cyclostoma elegans, pi. IV, f. 10, 11. 



Cyclostoma elegans, Drapernaud, p. 32, pi. 1 , f. 5 and 8 ; 

 Lamarck, An. San. Vert., VI, pt. 2nd, p. 148; PfeifFer, p. 74, 

 pi. 4, f. 30, 31 ; Brown, lUust. Conch., p. 34, pi. 14, f. 28; lb.. 

 First Ed., pi. 41, f. 28 ; Turton, Man., p. 93, f. 75 ; Fleming, 

 Brit. An., p. 257; Alder, Mag. Zool.and Bot,, II, p. 112; Brard, 

 p. 103, pi. 3, f. 7, 8; Jeffreys, Linn. Tr., XVI, p. 63; Thompson, 

 Ann. and Mag. Nat. Hist., VI, p. 51 ; Cyclostomus elegans, De 

 Montfort, II, p. 287 ; Turho elegans, Montagu, Test. Brit,, p. 

 342, pi. 22, f. 7 ; Maton and Racket, Linn. Tr., VIII, p. 167; 

 Brown, Wernerian Mem., II, p. 522 ; lb., Ency. Brit., VI, p. 



