576 PROCEEDINGS OF THE SAINT LOUIS MEETING 



periodical floods each summer sufficient to cover the whole region occupied by the 

 great body of the loess and the presentation of a theory that would seem to harmo- 

 nize all the facts. 



Remarks were made by B. Shimek, J. E. Todd, and the author. The 

 paper is published in the American Geologist, volume xxxiii, 1904, pages 

 205-222. 



The last paper presented was the following : 



FRESH-WATER SHELLS IN THE LOESS 

 BY B. SHIMEK* 



[Abstract] 



1. A review of the available literature in which reference is made to the occur- 

 rence of fresh -water shells in the American loess, with a discussion of the signifi- 

 cance and weight of such testimony, showing that as 'yet no well-authenticated 

 cases of the occurrence of fluviatile shells, at least in original loess, are known. 



2. A statement of the author's own experience in the study of loess mollusks, 

 which shows that land shells greatly predominate, and that only such fresh- water 

 forms as inhabit temporary small ponds and streamlets occur in the loess, and these 

 in relatively small numbers. 



In discussion remarks were made by G. F. Wright, Robert Bell, J. E. 

 Todd, and the author. 



The remaining papers of the program were read by title, as follows : 



COMPARISON OF THE STRATIGRAPHY OF THE BLACK HILLS, BIGHORN MOUN- 

 TAINS, AND ROCKY MOUNTAIN FRONT RANGE 



BY N. H. DARTON 



The paper is printed as pages 379-448 of this volume. 



NOTES ON THE GEOLOGY OF THE HELLGATE AND BIG BLACKFOOT VALLEYS, 



MONTANA 



BY N. H. WINCHELL 



[Abstract'] 



The following is a provisional general section of the rocks of the region in 

 descending order: 



1. The early Pleistocene is recorded in the most of the region only by the valleys 

 eroded and by the terraces along the valleys, but in the region of Placid lake is 

 a sheet of recent glacial deposits. This drift evidently was brought from the north 

 by glaciers that occupied the valley between the Mission range and the Rocky 

 Mountain range. 



2. Calcareous tufa, containing chert and fossil leaves. At numerous places tufa 

 of this kind is found, and sometimes it is very thick and massive. The flint 

 nodules have been used by the aborigines in making their implements. 



introduced by S. Calvin. 



