iv LIFE OF THE PLEISTOCENE 



cular interval has often been attended with great difficulty on account of the 

 ambiguity concerning its stratigraphic position — its relation to a distinct and 

 well known drift sheet. In some cases only a suggestion has been made, while 

 in many others not even this has been possible. Not a few records, however, 

 have been of such a character as to leave little or no doubt concerning their 

 relation to one of the drift sheets. Only such have been available for recon- 

 structing the life of these intervals. Many of the references are not available 

 because of gross errors of identification, as well as of stratigraphy; such as 

 Aughey's list of Missouri loess mollusks, which is worthless for this reason. 

 In all lists the modern nomenclature is used. 



In correlating these records with the particular interglacial interval in 

 which they are supposed to belong the writer has used his judgment, based on 

 the original stratigraphical data or upon some later local geological map or 

 record. It is probable that this judgment has not in all cases been correct. 

 In the list of biotic remains all groups of animals and plants (excepting the 

 Diatomaceae) have been included, in order that a comprehensive view might 

 be presented of the life of each interval. The lists of species at the end of the 

 volume (Chapter XIII) are so meager that they pitifully expose our lack of 

 knowledge and indicate forcefully that much is yet to be done before we are 

 in a position to write intelligently on the life of the Pleistocene. 



The title of this volume may be thot to be too inclusive, the region from 

 which the data have been gathered forming but a part of the entire territory 

 in which Pleistocene animals and plants have been found. It was thot, how- 

 ever, that the only way in which a knowledge of the life of the interglacial inter- 

 vals could be obtained would be to study the life which had been entombed 

 between the till sheets, and which could only have lived during the interval 

 represented. For this reason the area selected for study includes only that 

 part of the United States and Canada (east of the Rocky Mountains) that was 

 covered by the great continental ice sheets. Deposits outside of this area, 

 therefore, cannot be included, except for purposes of comparison, as there is no 

 way of deciding just which interval they may represent. In fact, many of the 

 records beyond the glaciated territory represent deposits which were forming 

 continuously thruout the entire time of the Pleistocene, they not being greatly 

 influenced by the great ice sheets. With this statement of the purpose of the 

 work, it is easily seen that the title "Life of the Pleistocene" is not inappro- 

 priate. 



Acknowledgments 



The writer is greatly indebted to many persons, professional and others, for 

 assistance during the preparation of the work. Chief among these may be 

 mentioned Dr. T. C. Chamberlin and Dr. Rollin Chamberlin, of the University 



