94 VERTIGO. 



thus described: " Shell differing from recent gouldii in being 

 more ventricose, especially on the last whorl, having the apical 

 whorls wider and more obtuse, the outer lip more auricled 

 causing the aperture to have its longest diameter more 

 diagonal than in gouldii; there are five denticles placed as in 

 gouldii, but more delicate than in the typical form ; the palatal 

 denticles are long and subequal. 



" Length 2.00; diameter 1.3 mm. Holotype. 



" Length 2,00; diameter 1.3 mm. Paratype. 



" Length 2.1; diameter 1.1 mm. Paratype." (Baker). 



Illinois: 31/2 miles east and 1% miles south of Lewistown, 

 Fulton County (Liverpool township), in loess of Peorian age. 

 Types: Museum Natural History, University of Illinois, No. 

 P2366. Paratypes, Acad. Nat. Sci. Phila., No. 145107. 



Vertigo gouldii loessensis F. C. Baker, Nautilus, Vol. 41, 

 April, 1928, p. 135 ; Trans. Illinois State Acad. Sci. Vol. 21, 

 1929, p. 297 (Aftonian to Early Wisconsin loess). 



" This Vertigo has been listed as goiddii but is different 

 from the typical species as living today. It has also been 

 listed as ventricosa, and some small, wide specimens do re- 

 semble this species. Loessensis strongly resembles Vertigo 

 elatior Sterki, and Sterki has referred certain forms found in 

 loess at New Harmony, Indiana to this species. They lack 

 the strong palatal callus so characteristic of elatior and are 

 the same as the Illinois variety here differentiated. It is 

 probable that the Vertigo listed as goiddii by Hanna (Kansas 

 Science Bull. VII, p. 120, pi. 18, fig. 4) is also this variety. 

 It is found in the Pleistocene from Yarmouth to Early Wis- 

 consin time. The form is here considered a marked variety of 

 gouldii but it might be advisable to consider it a distinct 

 species." {Baker). 



A paratype of loessensis is figured. It resembles V. elatior 

 in having a longer spire than V. vemtricossa. The palatal 

 folds of elatior stand on a more or less thick but variable 

 callus. It is very thin in some Maine examples, heavier in 

 those from Ohio. This palatal callus is distinctly developed 

 in paratypes of loessensis, which does not appear separable 

 from elatior. 



