70 VERTIGO. 



Staurodon LOWE, Proc. Zool. Soc. 1854, p. 214, type 

 P. pygmcca Drap. Not Staurod&n Lowe, 1852. 



Dexiogyra STABILE, Moll. terr. Viv. du Piernout, 1864, p. 

 104 (in Atti della Soc. di Scienze Nat., Milano, vi), for V. 

 moulwisia/na, V. pygni<ra, V. antivertigo. V. antwertigo here 

 designated as type. 



Dexiogira De BETTA, Moll. Prov. Veron., 1870, p. 83. 



Nearctula STERKI, Nautilus vi, 1892, p. 5, type by orig. des., 

 F. calif ornica Rowell. 



Haplopupa PILSBRY, Nautilus xi, Feb. 1908, p. 119, mono- 

 type V. dallicm-a,. 



Pupa DRAPARNAUD, 1801, and of many subsequent authors. 

 Not Pupa Bolten, see Vol. XXIV, p. 267. 



Small, oval, oblong or ovate, compact Pupillids, the summit 

 very blunt ; usually glossy and some shade of brown. Aper- 

 ture having the typical six teeth of Pupillidae, none of them 

 concrescent, part or all of them sometimes wanting; angular 

 lamella not marginal when present. Outer lip straightened or 

 bent inward in the middle. Animal without inferior tentacles. 



Type, V. pusitta. Mull. 



The apertural teeth of Vertigo show great modifications in 

 number and size. There are often small teeth accessory to 

 the six typical ones, and in other forms there has been re- 

 duction of teeth, the basal, angular and upper palatal being 

 lost in many species. Other forms have gone further, tooth- 

 less species resulting from degeneration of teeth in several 

 phyletic lines within the genus in both Europe and America. 

 These modifications make a diagnosis of the genus almost im- 

 possible. 



These teeth, though among the best specific characters, are 

 subject to wider variation than usual. The secondary den- 

 ticles are especially likely to vary ; but also the basal fold, the 

 angular lamella and often the upper palatal fold are variable, 

 being either present or absent in many species. 



In many Vertigos the basal fold is subcolumellar in position, 

 rather than on the basal margin at the foot of the columella. 

 Tt has therefore often been counted as a second columellar 

 tooth in descriptions. 



