TERTIARY MAMMAL HORIZONS. 25 



European geologists and inv^ertebrate palaeontologists are 

 practically unanimous as to these divisions (Deperet, '92). Cer- 

 tain vertebrate paleontologists, however, still include in the 

 uppermost Miocene the Pikermi and Eppelsheim beds which 

 clearly belong in the base of the Pliocene. Faunally (mam- 

 mals) the Miocene is now divided into upper and lower but it is 

 apparent that it is capable of division into three life-stages typi- 

 fied in France as follows : 



3. Upper, typified by Grivc-St-A/baii. 



2. Middle, typified by Sajisan and Siuiorrc. 



I. Lower, typified by Sables dc l' Orlca)iais. 



The separation of these life stages we owe chiefly to Deperet. 



Physical Geography. — The Miocene is in general distin- 

 guished by a relative elevation of Northern Europe and depression 

 of Southern P^urope ; accompanied by great volcanic eruptions 

 in central France and Hungary ; and ending in the completion 

 of the great chains of Alps and Himalayas. 



I. Langhien. In France the Oligocene Lake Basins were 

 drained off and replaced by great river valleys, as attested by the 

 fluviatile deposits ov Sadies de TOrleanais. 2. Helve tie n. This 

 stage has a thickness of 495 metres in the basin of Crest (Fon- 

 tannes.) The sea invaded the west coast of France up the valley 

 of the Loire, also upon the south, isolating Spain and extending 

 up the Rhone Valley, surrounding the northern slope of the Alps 

 and extending northward to the Mayence Basin, to the east and 

 south into the Vienna Basin, submerging large parts of Austria 

 and Italy and converting parts of Europe into an archipelago. 

 3. Tortonien. A general recession of the sea accompanied by a 

 marked increase in the number of freshwater deposits characterize 

 this stage. Among these deposits perhaps the most typical or 

 complete at the present time is that of Grive-St-Alban (Isere), 

 monographed by Deperet ('92). The lesser part of this fauna is 

 equivalent to that of Sansan ; the greater part is somewhat newer- 

 To the southeast, Austria was still partly submerged forming the 

 Leithakalk or marine summit of the Tortonien in the Vienna Basin. 



Climate. — If we can judge by the very gradual evolution of 

 the fauna, the physical and biological conditions changed slowly. 



