EVIDENCE THAT BEDS ARE AETONIAN 131 



heavy-shelled Unio) in which the shells were closel}' massed. They were 

 very fragile and could not be taken out entire. With them were shells of 

 iS pKcErium sulcatum and a shell of Ancylus rivularis. Several large" 

 bouldei-s rested on this gravel layer. 



The finer sand contained the following mollusks : 



Unio , fragments. Segmentina armigera. 



Sphcerium sulcatum. Physa , fragment. 



Pisidium . Ancylus rivularis. 



Valvata tricarinata. Succinea retusa. 



Planorhis Mcarinatus. ' Succinea dvara. 



Planorhis dilatatus. 



8. Ordway well. — This well was excavated on the same terrace-like 

 slope, about an eighth of a mile northeast from the pit. 



Measurements of the well section could not be made, but it was plain 

 that the Kansan reaches the surface here, and may be traced upward for 

 30 feet more (vertically) before it disappears under the loess which covers 

 the ridge in its upper parts. In the well itself bluish Kansan till was 

 clearly discernible. Below this Aftonian sand, with a little gravel, rested 

 on a deep bed of l^ebraskan drift. The man who dug the well claimed 

 to have bored into the blue-black '^^hard-pan" (N'ebraskan drift) to a 

 total depth of 175 feet. 



An examination of the materials brought up from the well corroborated 

 the correctness of the record. The sand is here clearly interglacial, lying 

 between the Kansan and the Nebraskan drift sheets, and hence Aftonian. 



The sand in the well section yielded the following fossils : 



TJnio , fragments. Valvata tricarinata. 



Sphcerium sulcatum. PlanorMs Mcarinatus. 



Pisidium -r . 



Some years ago a fragment of a large scapula was obtained from an old 

 gravel pit near this well, and it has been added to the collection (number 

 91). 



9. Griffin well. — This is located near Mapleton, Iowa, on the farm of 

 C. H. Griffin, on the east side of section 17, township 85 north, range 

 xlii west. It is situated in a rolling Kansan area about 50 feet above the 

 valley of Heisler Creek. 



The section was made through loess, Kansan drift, and into Aftonian 

 sand and gravel to a depth of about 40 feet. The writer examined the 

 material taken from the well. Moreover, Kansan appears at the surface 

 on the same slope at a lower level, the loess covering only the upper parts 

 of the ridge. At a depth of 35 feet a part of the tooth of Elephas im- 

 perator was found in .the gravel. 



