

254 LIFE OF THE PLEISTOCENE 



the Sangamon or post-Illinoian interval. Shimek (Bull. Geol. Soc. Amer., 

 XXI, page 139) states that Witter's specimen was a fragment of a molar of 

 Elephas primigenius from a layer of Aftonian gravel one foot thick. 



At Des Moines, a loess occurs between the Kansan and Wisconsin drifts, 

 which contains a large and varied molluscan fauna All are apparently refer- 

 able to the post-Kansan interval. 32 (Modern names used.) 



Gallba humilis modicella Strobilops labyrinthica (perhaps virgo) 



" obrussa ( = desidiosa) Euconulus fulvus 



Caryckium exiguum {exile, vide Shimek) Helicodiscus parallelus( = linealus) . 



Succinea obliqua Vallonia pidchella 



" avara (gracilicosta, vide Shimek) 



Polygyra clausa Zoniloidcs arborea 

 " midtilineata " minuscula 



" thyroides? Bifidaria pentodon 

 " monodon " armifera 



Pyramidula altemata " corticaria 



" slrigosa { = Ore.ohelix iowcnsis)Pupilla muscorum 



" striatella Vertigo ovata 



( = cronkhitei anthonyi) Helicina occulta 



Bain 33 lists the fauna of Des Moines, indicating that the loess underlies 

 Wisconsin drift, and adds five species. 



Zonitoides shimeki (= Pyramidula shimeki) 



Pupa blandi ( = Papilla blandi) 



Vertigo simplex (—Sphyradium edenlidum alticola) 



Cochlicopa lubrica 



Limnaea caper ata ( = Galba caperata) 



Pyramidula slrigosa iowensis ( = Oreohelix iowensis) 



A post-Kansan loess underlies the Wisconsin drift in Storey County A 

 good exposure has been observed, in Washington Township, along Clear and 

 Walnut creeks, the latter showing the following section: 34 



Drift, yellowish above, bluish below (Wisconsin) 20 feet 



Loess, sandy below (post-Kansan) 20 " 



Clay, blue with much coarse gravel (Kansan) exposed. 



The upper four feet of the loess is stained yellow-brown along joint planes, 

 and grades downward into massive, structureless, pale blue clayey silt con- 

 taining, in places, an abundance of root casts, wood fragments and black 

 carbonaceous spots, and emits a distinct swamp-like odor. The entire deposit 



32 McGee and Call, Amer. Journ. Sci., (iii), XXIV, pp. 202-223 (list p. 216). 



33 Geol. Iowa, VII, p. 344. 



34 Beyer, Proc. Iowa Acad. Sci., VI, p. 118. 



