THE NEBRASKAN ICE INVASION 235 



A tusk and tooth of a mastodon have been found in eighteen Mile Creek, 

 Franklin County, but the horizon is doubtful, altho it may have been Afton- 

 ian. 68 The same holds true of the horn-core of Bison atteni, which was fished 

 from the bed of the Big Blue River, a few miles from Manhattan, Riley 

 County. 69 This was at first referred to Bison latifrons. 



In Linn County , 69a in coal shaft number 2, three and one-half miles south- 

 west of Biocourt, in the valley of the Marias des Cygnes, the skull of Cas- 

 toroides was found at a depth of 34 feet in a layer of sedimentary material of a 

 bluish color overlying a deposit of sandy conglomerate. The deposit is be- 

 lieved to be the same as that at Trading Post, which was above a conglomerate 

 and contained bones of elephant, horse, camel, etc. A section at Trading Post 

 exhibited the following strata (p. 391): 



Black loam 6 feet 



Marly clay 12 



Blue and yellow marl, verging into shale 12 " 



Bluish silt, with bones \ l /z " 



Conglomerate, lying on the heavy Bethany Falls limestone l l / 2 " 



Height of section 33 " 



The deposit at Biocourt is believed to be Aftonian and the skull has been 

 named Castoroides kansensis. 



5. South Dakota 



In South Dakota, Castoroides 10 has been recorded by Calvin from Sioux 

 Falls. Todd 71 reports wood from wells in the lower part of the till which he 

 refers to a preglacial or circumglacial forest. It is probably an Aftonian forest 

 overriden by the Kansan ice. A section three and a half miles west of Fair- 

 view, Lincoln County, on the Big Sioux River, apparently includes the Afton- 

 ian. 72 The section is shown below: 



Loess 6-10 feet. 



Till with irregular stratified sand strata toward the bottom. The lower 20 



feet is blue and almost free from pebbles 100-110 feet. 



Fine sand with large rusty concretions of upper portions and a few fragments 

 of large, pearly shells (Unios). The stratum is of undeterminable thick- 

 ness 20 feet 



Unexposed. Probably much of it is a pebbleless clay of Cretaceous age 1 10 feet. 



The sand containing Unios is apparently referable to the Aftonian interval. 



"Wheeler, Trans. Kansas Acad. Sci., VI, p. 11. 



89 Mudge, op. cit., V, pp. 9-10; Hay, Iowa Geol. Surv., XXIII, p. 326. 



• M Martin, Kansas Univ. Sci. Bull., VI, No. 6, pp. 389-396, 1912. 



70 Bull. GeoL Soc. Amer., XXII, p. 215. 



71 Bull. 158, U. S. Geol. Surv., p. 121. 

 11 Op. cit., p. 83. 



