ORIGIN AND DISTRIBUTION OF MAMMALS 303 



Pliauchenia. Apart from the presence of the edentates, which arrived from 

 South America, this fauna is characterised by the complete disappearance of the 

 Agriochoeridae and Ehinoceridae. The deposits with Elephas imperator in Texas 

 and Mexico may also perhaps be assigned to the Pliocene. 



Pleistocene. 



The Pleistocene begins both in North America and in Europe with a fauna 

 which still contains species of a warm climate and even extinct genera. In 

 North America the Sheridan formation of Nebraska and the Rock Creek beds 

 of Texas are characterised by the first appearance of the genera Eqmis, Anlilo- 

 capra and Castoroides, with Elephas, Platygonus, Eschatius, Camelojjs, Felis, Ccmis, 

 Lutra and Mylodon ; while the Merijcodus-\\\s.e, Cap)roin('ryx has become extinct, 

 and the rodents, except Castoroides, are represented only by existing genera. In 

 Europe we find the oldest Pleistocene mammal fauna in the Cromer Forest 

 Bed of England and Holland, at St. Prest (near Chartres), and at Mauer, near 

 Heidelberg : the latter locality has become especially famous by the discovery 

 there of a very primitive human jaw. The latest researches among the 

 mammals found in these localities have shown, that between the Pliocene and 

 Pleistocene there is no such sharp line of demarcation as might be supposed, 

 for we still meet here with Pliocene species such as Hippopotamus major, Equus 

 stenonis, Rhinoceros etruscus, Elephas meridionalis, Ursus arvernensis, Canis neschers-. 

 ensis. Lynx issiodorensis and Hyaena arvernensis. Some of these species, indeed, 

 persist into the somewhat younger fauna of Mosbach, near Mainz, where they 

 are associated with Capreolus caprea, Cervus elaph.us, Alces latifrons. Bison priscus, 

 Sus scrofa and Castor fiber, which then, with the exception of Ursus deningeri and 

 Alees latifrons, reappear in all the younger Pleistocene deposits formed during 

 a warm period, such as those of Taubach, Krapina, and the caves of Mentone. 

 With them there also occasionally occur Inuus, Hipp)opotamus, and Machairodus 

 latidens, as well as Hyaena striata. In Asia (China) during the older Pleistocene, 

 Hyaenardos and Chalicotherium, and a large tapir, still lived with Rhinoceros 

 sinensis and B. plicidens, which to some extent represent the European 

 mercki, also Elephas namadicus, hyaena, deer, and pig. To the older Pleistocene 

 are also referable the fauna of the Narbada valley in India and the fauna 

 of Trinil in Java, which has become so famous by the occurrence of Pithec- 

 anthropus, with Macacus, Biececyon, Feliopsis, Stegodon, Rhinoceros, Hippopotamus, 

 Sus, Cervulus, Axis, Duhoisia (related to Boselaphus), Buffelus and Bibos, all of 

 which are represented only by extinct species sufficing to indicate the great age 

 of this fauna. 



In North America the true Middle Pleistocene appears to be characterised 

 by the disappearance of Camelus, Arctotherium, and Elephas columbi, and their 

 replacement by Elephas primigenius. Mastodon, Odocoileus, Haploceras, Bison, 

 Alces, Ovibos, Rangifer, Cervus and Ursus; though at first there still occur 

 machairodonts, Megalonyx, Mylodon, Equus, Tapirus and Mylohyus. A fauna of 

 this period seems to be found in the famous Port Kennedy cave in Pennsyl- 

 vania, perhaps also in the marls of western Kansas. Megalonyx and Nothro- 

 therium, as well as Equus and Elephas, are also found in the Potter Creek cave 

 in California, and at Silver Lake in Oregon. Most of the mammal remains, 

 however, belong to still existing species of carnivores, rodents, deer and bison, 

 among which indeed Mastodon americanus appears for the first time. Peculiar 



