106 BRITISH MOLLUSKS. 



1. Balea perversa. Reversed Balea. 



Shell ; sinistral, minutely unibilicated, conically turreted, fulvous- 



olive, very thin, horny, semitransparent, 



glossy, crossed irregularly with opake, whi- 

 tish lines, whorls seven, rather flatly convex, 



beneath the lens minutely wrinkle-striated, 



rather impressed at the sutures, last whorl 



sometimes furnished with a small callosity 



or lamella; aperture pyriformly subquadrate, 



lip thin, simple, slightly reflected, sinuous 



above, dilated over the umbilicus. 

 Turbo perversus, Linnseus (1758), Sgst. Nat. 10th edit. p. 767. 

 Bulimus perversus, Poiret (1801), Coq. de VAisne, Prod. p. 57. 

 Pupa fragilis, Draparnaud (1801), Tail. Moll. p. 64. 

 Clausia parvula, Gsertner (1813), Conch. Wetter, p. 22. 

 Odostomia perversa, Fleming (1814), Edin. Encgc. vol. vi. p. 76. 

 Clausilia fragilis, Studer (1820), Kurz. Verz. p. 89. 

 Helix perversa, Ferussac (1822), Tall. Sgst. p. 66 (not of Linnaeus). 

 Balea fragilis, Prideaux (1824), Zool. Journ. vol. i. p. 61. pi. vi. 

 Balea perversa, Fleming (1828), Brit. Anim. p. 271. 

 Fusulus fragilis, Fitzinger (1833), Sgst. Verz. p. 105. 

 Clausilia perversa, Charpentier (1837), Moll. Suiss. p. 17. 

 Pupa perversa, Potiez and Michaud (1838), Gal. Moll. Douai, p. 166. 

 Eruca fragilis, Swainson (1840), Treat. Malac. p. 334. 

 Clausilia uniplicata, Calcara (1840), Effem. Sicil. p. 82. 

 Stomodonta fragilis, Mermet (1843), Moll. Pgr.-Occid. p. 48. 

 Pupa (Balea) perversa, Moqiun-Tandon (1855), Hist. Moll. vol. ii. p. 349. 



pi. xxv. f. 6 to 14. 

 Hab. Throughout Europe. Azores. Madeira. (Among moss and lichens 



in crevices of walls, rocks, or trees.) 

 The shell of Balea perversa may be readily distinguished from 

 those of Bulimus, Clausilia, or Pupa, by its simple sinistrally coiled 

 form of seven whorls, and glossy fulvous horny substance, scarcely 

 striated, but characteristically marked in the direction of the lines 

 of growth with irregularly developed whitish opake lines. There 

 is no contraction of the last whorl, and no indication of teeth or 

 winding plaits in the aperture. The only appearance of internal 

 sculpture is the occasional presence of a small callosity or lamella 

 on the body-whorl. The lip is thinly, very thinly, reflected, and it 

 is just sufficiently sinuated to impart a squarish contour to the 

 aperture. 



