124 
IOWA ACADEMY OF SCIENCES. 
the region in 1884, and later, during the season of 1897. Allu- 
sion is made to former observations in Bulletin No. 1, of 
the South Dakota Geological Survey. In the grading of 
streets in Sioux Falls, at several points, a dark band resem- 
bling soil was noted. This is true more particularly north 
and west of the brewery. This band was first explained 
by the writer, as marking a temporary flood-plain of the 
Big Sioux during some stage of the occupation of the outer 
moraine He was unable to find evidence of its extending very 
far from the stream. The soil was underlain by till, and also 
overlain by that which seemed to be of nearly the same age. 
During the recent visit, not only were these localities re- 
examined, but others, developed by more recent grading, were 
observed near the postofiice, and a more notable example was 
found a mile or more northeast of the postofiice, in cuts 
along the Illinois Central railroad. At the latter point, there 
were found distinct traces of a buried pond, somewhat like a 
basin of the present. In its deeper portions, there is a depth 
of several feet of dark soil, containing numerous fresh-water 
shells — Valvata, Planorbis, Limnea, and also fragments 
of a cervical vertebra of a large vertebrate; fragments of 
turtle-shell, resembling the common mud-turtle in appearance 
and size, and two or three small bones, apparently of an 
animal about the size of a rabbit. The visit was brief, and 
further investigation w’ould doubtless reveal more fossils. The 
vertebrate remains were submitted to Prof. William B. 
Scott, of Princeton, who determined the largest to be a cervi- 
cal vertebra of a horse. The other bones were undetermin- 
able. 
Through the thoughtfulness of Mr. Bain, a series of the 
shells was submitted to Professor Shimek, in time to have his 
determinations for this paper. His report is as follows: 
“The following are from the Illinois Central railroad cut 
east of Sioux Palls, S. D, : 
“1. Planorbis biGarinatus Say. 
“2. Planorbis parvus Say. 
“3. Pliysa heterostropha (Say) Say. 
“4. Limnea caperata Say. 
“5. Valvata tricar inata Say. 
“6. Splicerium sulcatum (Vdon..) Prime. 
“7. Pisidium, compressum Prime. 
“8. Vallonia costata (Mlill.) Ster. 
