116 BRITISH MOLLUSKS. 



1. Vertigo antivertigo. Unreversed Vertigo. 



Shell ; minute, tumidly cylindrical, compressly umbilicated, chest- 

 nut or fuscous horny, semitransparent, glossy, 

 whorls four to five, convex, smooth ; aperture 

 triangularly heart-shaped, with from six to 

 nine small teeth, lip thin, rather expanded. 



Vertigo sexdentata, Studer (1789), Faun. Helv. in Coxe, 

 Trav. Sivitz. vol. iii. p. 432 (without characters). 



Pupa antivertigo, Draparnaud (1801), Tail. Moll. p. 57. 



Turio sexdentatus, Montagu (1803), Test. Brit. p. 337. 

 pi. xii. f. 8. 



Vertigo sexdentatus, Ferussac (1807), JEss. Meth. p. 124. 



Odostomia sexdentata, Fleming (1814), Edin. Encyc. vol. vii. part 1. p. 76. 



Pupa octodentata, Hartmann (1821), JYeue Alp. vol. i. p. 219. 



Vertigo septemdentata, Ferussac (1822), Tail. Syst. p. 68. 



Alcea palustris, Jeffreys (1830), Trans. Linn. Soc. vol. xvi. p. 360 and 516. 



Vertigo palustris, Leach (1831), Turt. Man. p. 104. 



Vertigo antivertigo, Michaud (1831), Comp. Drap. p. 72. 



Alcea antivertigo, Beck (1837), Ind. Moll. p. 85. 



Vertigo (Isthmia) palustris, Gray (1840), Turt. Man. p. 204. 



Pupa sexdentata, Fleming (1842), Brit. Anim. p. 262. 



Stomodonta antivertigo, Mermet (1843), Moll. Pyr.-Occid. p. 54. 



Vertigo (Isthmia) antivertigo, Moquin-Tandou (1855), Hist. Moll. vol. ii. 

 p. 407. pi. xxix. f. 4 to 7. 



Hai. Throughout Europe. Throughout England and Ireland. Channel 

 Islands. (In marshy places, on water flags, etc.) 



Although not more than about the twelfth of an inch in length, 

 the shell of this species is, with the exception of the Toothless 

 Vertigo (V. edentula) and V. Motclinsiana, which is scarcely yet 

 established as British, the largest of the genus. It is of a shortly 

 cylindrical tumid form of from four to five whorls, transparent and 

 glossy, with from six to nine teeth. The aperture assumes a tri- 

 angular form, and it has from two to three teeth at each angle. 

 The animal is of a dusky slate-grey colour, and, according to 

 Dr. Gray, has a couple of dots in place of a lower pair of tentacles. 

 M. Moquin-Tandon describes this little mollusk as carrying its 

 shell nearly straight when crawling, sHghtly balancing from right 

 to left. The very sombre colour of the animal gives to the trans- 

 parent shell a dark brown appearance. 



