INTRODUCTION 



The Pleistocene Period is of especial interest, as it corresponds to 

 one of those periods commonly looked upon as marking a break in 

 the geological record left man by fossils in the sedimentary rocks of 

 the earth. There is evidence to believe that there was a long period 

 of time between the last of the determined Paleozoic formations and 

 the first of the Mesozoic, and another long period between the last 

 of the Mesozoic and the first of the Cenozoic. Of these periods only 

 a partial record, in way of a few widely scattered deposits, has been 

 left. They are generally looked upon by geologists as periods of 

 great and rapid changes in life-forms. LeConte and others put 

 themselves on record as believing these periods of lost record, or at 

 least the first of them, to have been periods of considerable glacia- 

 tion, when, whatever deposits there were, were put down as drift 

 or some other product of glaciation in such condition as to be com- 

 pletely obliterated in the long periods which have since elapsed. 

 The Pleistocene, being evidently a period which was ushered in by 

 the advance of the ice from the north upon more southernly latitudes, 

 may throw some light upon these other periods of supposed glaci- 

 ation. And as the Pleistocene can be studied to some extent from its 

 fossiliferous deposits, one sees that the information gained from a 

 study of the Pleistocene may be of some value in interpreting the 

 probable conditions that existed during the periods of lost record 

 between the Permian and the Triassic, and between the Cretaceous 

 and the Eocene. So the Pleistocene has this interest in addition to 

 those inherent in itself. In this paper, however, there will be no 

 further mention of this particular phase of interest, but a study of 

 such phases as concern the Pleistocene more directly. 



Though deficient in those qualities which come by reason of respect 

 and veneration for age, the Pleistocene is of very great interest as 

 furnishing the link that connects the present life with the life of the 

 recent geologic past. It exhibits the process by which ocean bed 

 has been converted into dry land. It gives evidence of the descent 

 of living forms from fossil forms, since its fossil forms have very 

 many of their characters, even to the marking and colors of their 

 shells, almost as well preserved as those of their descendants living 



