372 LIFE OF THE PLEISTOCENE 



parts of the country. The two faunas were said by Cope to be contemporary 

 and to have lived during pre-Champlain time. After the Champlain time a 

 new fauna is thought to have appeared, consisting of existing species with a 

 few remnants of the pre-Champlain fauna. 



Osborn 5 recognizes four faunas, first, the Equus-Mylodon zone; second, the 

 Megalonyx zone; third, the Ovibos-Rangifer zone; and fourth, the Cervus 

 zone, the latter being the fauna immediately preceding the discovery of Amer- 

 ica by Columbus. The first two zones are thot by Osborn to be practically 

 contemporary, the Equus-Mylodon zone being, perhaps, a little earlier in ap- 

 pearance. Scott 6 follows Osborn in his treatment of Pleistocene mammals. 



These authors in these works have not taken into account the different 

 glacial advances and retreats, and the resulting interglacial intervals, and a 

 true picture of the vertebrate life of the Pleistocene can be gained only by a 

 study of the stratigraphy of the Pleistocene deposits in connection with the 

 biotic remains contained in these deposits, as has already been pointed out 

 by Hay. 7 The deductions of Cope, Osborn and others are mainly based on 

 material found in strata beyond the limits of the ice sheets, which cannot be 

 positively correlated with the glacial divisions of this period for obvious reasons. 

 Many other records are from cave deposits and bed rock fissures, which are 

 usually of doubtful age stratigraphically. Exact knowledge of the extent 

 and survival of Pleistocene mammals (as of other groups of animals and plants) 

 can be gained only by a study of material contained in interglacial deposits 

 of undoubted age. It will probably be possible to separate the Pleistocene 

 mammals into early, middle, and late zones or faunas. Dr. Hay 8 sums up 

 the situation based on our present knowledge in the following words: "It 

 looks, therefore, as if the earliest Pleistocene was characterized by the existence 

 of numerous edentates, horses, camels, tapirs, and saber-tooth cats, and few 

 bisons, while during the later pre- Wisconsin Pleistocene, there were few eden- 

 tates, few horses, no camels, few saber-tooth cats, but numerous bisons." 

 The tables presented in this chapter furnish evidence of the truth of this state- 

 ment. 



Extended analysis of the tables herein presented would be unwise in the 

 light of our present imperfect knowledge of the life of the different intervals. 

 Factors of stratigraphic differentiation must be found in the insects and mam- 

 mals, the plants and mollusks being of little value for this purpose on account 

 of their uniformity thruout the interglacial intervals. Plants, however, are 

 good indicators of climatic changes and have had, and will continue to have, 

 an especial value in placing the climate of the fauna which may be found 



s Age of Mammals, 1910, pp. 452-467; Hay, Smith. Mis. Coll., LIX, pp. 3-15. 



6 A History of Land Animals in the Western Hemisphere. 



7 Smith. Mis. Coll., LIX, pp. 3-16, 1912. 



8 Op. tit., p. 15. 



