124 IOWA ACADEMY OF SCIENCES. 



the region in 1H84, and later, during the season of 1897. Allu- 

 sion is made to former observ^ations 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 de^jth 

 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 would 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 Falls, S D. : 



1. Planorbis bicnrinatus Say. 



2. Phinorbis j)arvu-s Say. 



3. Physa heterostropha (Say) Say. 



4. Liiintea caperata Say. 



5. Vidvafa triGarinato (Say) Say. 

 •'6. Sp/Kcriuiii sulcation (Lam.) Prime. 



7. Pisidiinii coiiipressnm Prime. 



8. V((Uonia <x>sta fa (Mnll.) Ster. 



