EVIDE^sCE THAT BEDS ARE AFTOXIAX 127 



The following fossils were obtained from the Jensen well : 



212." Mammut mirificmu, 2 molars (see Bulletin of the Geological 

 Society of America, volume 20, plate 27). 



216. Cranial bones of the same species. 



217. Fragments of tusk of same species. 



221. Homologue of the first and second phalanges of sloth. 

 Unidentified fragments of bone. 



2. Searles section. — This is also a w^ell section, reinforced by an excava- 

 tion for a cellar near by. It is located a quarter of a mile west of section 

 (1) and at a point somewhat lower. 



The section as reported by Mr. Searles is as follows : 



Dark brown surface soil, 3 to 4 feet. 



Yellow clay, 12 to 13 feet. 



Blue joint clay with boulders, 1 to 2 feet. 



Sand, 2 feet. 



Gravel, about 6 feet. 



Shale, about 30 feet penetrated. 



The yellow clay is probably loess and Loveland joint clay, these two 

 usually being confused by well-diggers; the blue joint clay is evidently 

 Kansan drift ; the sand and gravel belong to the Af tonian, and the shale 

 is Cretaceous. 



The cellar, which is east of the well and a little lower, showed 4 to 5 

 feet of loess resting unconformably directly on a layer of gravel 1 to 2 

 feet in thickness, and this rested on fine sand. The sand and gravel are 

 evidently Aftonian, the former containing fragments of shells of SpJi ce- 

 rium, probably S. sulcatum. 



The conclusions concerning the identity of the several strata in sections 

 (1) and (2) are further strengthened by the fact that other sections in 

 this region show a corresponding arrangement. The best of these sec- 

 tions, so far as the writer observed, is that in the first cut along the Chi- 

 cago, Milwaukee and Saint Paul Eailway 2 miles north of Chatsworth 

 and about 8 miles north of the Jensen well. 



Here about 18 feet of loess rest on a mass of Loveland and typical Kan- 

 san drift which is separated from the underlying dark Cretaceous shale 

 by a distinct stratum of Aftonian sand and gravel. The Kansan and 

 Aftonian are unconformable and are separated by a strongly oxidized 

 ferruginous band. 



^ The numbers preceding the names of mammals in the lists included in this paper 

 are Museum numbers, the specimens being deposited in the Geological Museum of the 

 State University of Iowa. 



