4 PERISTOMIDA. 



2. Paludina achatina, pi. I, f. 6, 7. 



Paludina achatina, Lamarck, An. San. Vert., VI, pt. 2ncl, p. 

 174; Ency. Meth., pi. 458, f. 1, a,h; Rossmassler, p. 109, f* 

 66*; Turton, Man., p. 133, f. 119; Brown, Illust. Conch., p. 

 26, pi. 14, f. 68, 69 ; Lymnea vivipara, Fleming, Brit. An., p. 

 315; Cyclostoma achatina, Drapernaud, p. 36, pi. 1, f. 18. 



Shell thin, oblong-ovate, ventricose ; spire consisting of four 

 or five considerably inflated volutions, separated by a well de- 

 fined, deep suture, and terminating in a rather obtuse apex ; 

 aperture suborbicular, slightly contracted above, white within, 

 with the external bands apparent ; pillar lip a little reflected on 

 the columella ; outer lip thin, and sharp on the edge ; whole 

 shell covered with an olivaceous epidermis, beneath which it is 

 provided with three, dark reddish brown, spiral girdles on the 

 body, and two on the superior volutions; surface with a few 

 obsolete wrinkles, or lines of growth ; aperture provided with a 

 thin, elastic, horny operculum. 



Found in the canal at Birmingham, where it has hitherto 

 been mistaken for the P. vivipara. 



This species may be distinguished from the P. vivipara by 

 the volutions being less inflated, in the suture being less deep, 

 the spire tapering less abruptly, and more obtuse at the apex ; 

 and in the whole shell being more cylindrical. 



3. Paludina impura, pi. I, f. 8, 9. 



Paludina impura, Lamarck, An. San. Vert., VI, pt. 2nd, 

 p. 175; Brard, Coq. de Paris, p. 183, pi. 7, f- 2; Draper- 

 naud, Moll., p. 36, pi. 1, f. 19 ; Pfeiffer, p. 104, pi. 4, f. 40; 

 Brown, Illust. Conch., p. 27, pi. 14, f. 72, 73; Turton, Man., p. 

 134, f. 120; Alder, Mag. Zool. and Bot., II, p. 116; Paludina 

 tentaculata, Fleming, Brit. An., p. 315 ; Thompson, Ann. and 

 Mag. Nat. Hist., VI, p. 17 ; Helix tentaculata, Donovan, Brit. 

 Sh., Ill, pi. 93; Pennant, Brit. Zool., IV, p. 140, pi. 86, f. 140; 

 Montagu, Test. Brit., p. 389; Brown. Wernerian Mem., II, p. 

 531. 



Shell oblong-oval, thin, smooth, semitransparent ; spire con- 

 sisting of four or five ventricose volutions, deeply divided by 

 the suture, and terminating in an acute apex ; aperture subor- 

 bicular, pointed above, and closed by a testaceous, concentrically 

 wrinkled, operculum, which is internally coated with a testaceous 

 covering, and its nucleus subccntral ; outer lip smooth on the 



