IOWA ACADEMY OF SCIENCES. 
105 
were subjected to extremely desiccating conditions, were found 
after this experience, creeping about in their prison, seemingly 
perfectly contented. Yet we are sometimes told that the 
Succineas are all ‘‘semi-aquatic,” or that they must have an 
abundance of moisture. Another illustration, equally striking, 
is furnished by the writer’s experience and observations at 
Council Bluffs during the past summer and autumn. It had been 
purposed to make a detailed comparative study of the fossil 
and modern molluscan faunas of that vicinity, but the work 
was somewhat interrupted by the severe September rainstorms 
and November blizzards. Nevertheless interesting and valu- 
able data were obtained, and are here briefly presented. 
More than 4,000 fossils were collected, and their distribution 
was carefully noted, in twenty exposures, beginning at the 
eastern extremity of Fifteenth avenue in Council Bluffs, thence 
along the bluffs to the high school, — a distance of about one 
mile, — and in Fair mount park, along its winding roads, for about 
half a mile eastward. The location of the several exposures is 
shown on the accompanying map. A list of the fossil species, 
together with the number of specimens collected in each 
exposure, is given in the appended table. 
If this table is studied it will be observed that of the thirty 
species collected, not one is aquatic. 
For purposes of comparison the writer made collections of 
recent shells in seven distinct localities in practically the region 
containing the above-noted exposures. These localities are 
here discussed in detail, the letters designating them being also 
employed to mark them on the map. 
A. A grassy, treeless hillside in Fairmount park, nearly 
opposite Eleventh avenue, and at an altitude of from 
175 to 245 feet above the river valley.* Species 8, 11 
and 29 f were found living. 
B. A grassy, treeless slope just above the exposure marked 
N. Altitude about 200 feet. Species 8, 10, 11, 15 and 
29 were found. 
G. Near the Tenth avenae entrance to Fairmount park, at 
an altitude of about ninety feet above the river plain. 
Species 8, 10, 11, 21, 22, 27 and 30 were found. A 
few stunted and scattered Bur-oaks grew on the slope 
immediately above this point. 
*The altitudes were all determined by barometric measurements taken from the 
nearest north and south street on the river flat. 
+The numbers refer to the species named in the table of fossils. 
