IOWA ACADEMY OF SCIENCES. 103 



Helicina occulta Say (common). 

 Pupa alticola Ingersoll. 

 Pyramidula striatella Anthony. 

 Succinea avara Say. 



Similar deposits, though without fossils, occur under the 

 drift in the bluffs east of Cordova in Illinois, and in the north- 

 ern part of the city of Clinton in Iowa. At the latter place 

 they are finely laminated and are associated with a peaty or 

 soil-like layer. A deposit which appears identical with the 

 loess -like silt on Thirty -fifth street in Rock Island is found 

 underlying the till on the east line of section 12, T. 17 N. , and 

 R. 1 W. south of the city, and also in a gully near the bluffs of 

 the Mississippi river in the west end of the county on section 

 31, T. 16 N., R. 5 W. At the former place it rests on the coal 

 measures and contains in about the same relative abundance 

 the same fossils that were found in the silt exposed on Thirty- 

 ninth street in the city. In the exposure in the west end of the 

 county the underlying beds are not seen. The total thickness 

 of the drift above it is about 100 feet. Shells are abundant and 

 they are of the same kinds and of the same relative frequency 

 as at the former place. The following species have been iden- 

 tified by Dr. W. H. Dall of the U. S. National museum: 



Helicina occulta Say (abundant). 

 Hehcodiscus lineatus Say. 

 Limncea humils Say 

 Pupa armifera Say. 

 Pyramidula perspectiva Say. 

 Pyramidula striatella Anthony. 

 Strobitops labyrinthka Say. 

 Succinea avara Say. 

 Succinea luteola Gould. 

 Polygyra, sp. 

 Vitraea arborea Say. 



These loess-like deposits have a bluish-green color in fresh 

 exposures, but one season of weathering gives them a reddish- 

 gray hue to the depth of one or two feet and then their resem- 

 blance to the loess in color, as well as in structure, is quite 

 marked. Even the tubular ferruginous concretions of the 

 latter deposit appear. 



The precise relation of the soil beds to this deposit and to 

 the laminated silts, with which it seems to be associated, and 



