OF WESTERN NORTH AMERICA. 



87 



The divisions of the inid-Pleistocene will ultimately be clearly 

 marked off, first by the successive disappearance and extinction of 

 the less hardy lower Pleistocene forms, second by the appearance or 

 invasion of the more hardy modernized forms. 



The following table is merely approximate: 



Order of appearance and disappearance of lower Pleistocene forms. 



APPEARANCE. 



Early Pleistocene 



Mylodon (central). 

 Paramylodon. 

 Platygonus. 

 Elephas columbi. 

 Antilocapra. 

 Camelus. 



Mid-Pleistocene. 



Elephas primigenius. 

 Mastodon. 

 Odocoileus. 

 Haploceras, 

 Erethizon. 

 Bison. 

 Alces. 

 Ovibos. 

 Cervus (late). 

 Ursus (late). 

 Rangifer (late). 



EARLY PHASES OF THE MIDDLE PLEISTOCENE. 



The earliest phase, corresponding with the earliest mid-Pleisto- 

 cene of Europe, is probably at present unrecognized in America. 

 Other early phases of the middle Pleistocene may be provisionally 

 distinguished as follows: (1) The true European stag Cervus does 

 not appear; (2) the Camelidae, Equidse, Tapiridse, Edentata-Gravi- 

 grada, and Elephantidse still survive; (3) many extinct species of 

 modern genera and many surviving modern species appear. 



Port Kennedy cave, Pennsylvania. — The Port Kennedy cave ^ has 

 yielded 54 species of mammals, 40 of which are now extinct. From 

 an analysis of its fauna, Bamum Brown ^ is inclined to place it in the 

 early part of the mid-Pleistocene. The climate was apparently 

 temperate. (1) It lacks the early Pleistocene genera Elephas and 

 Camelus, but the latter has thus far not been found in eastern deposits 

 at all. (2) Among surviving lower Pleistocene forms it includes (a) 

 of the Machserodontinae, 2 species; (6) of the Edentata, 2 genera, 



a Mercer, H. C, The bone cave at Port Kennedy, Pennsylvania: Jour. Acad. Nat. Sci. Philadelphia, 

 vol. n, pt. 2, 1899. 



''Brown, Barnum, The Conard fissure, a Pleistocene bone deposit in northern Arkansas: Mem. Am. 

 Mus. Nat. Hist., vol. 9, 1908, pp. 157-208. 



DISAPPEAR.\NCE. 



Early Pleistocene. 



Elephas imperator. 



Capromeryx. 



?Paramylodon. 



Mid- Pleistocene. 



Camelus. 



Mylodon. 



Megalonyx. 



Tapirus. 



Arctotherium. 



Elephas columbi. 



Elephas primigenius. 



Upper mid-Pleistocene. 



Smilodontopsis. 

 Mastodon. 

 Equus. 

 Mylohyus. 



