TERTIARY MAMMAL HORIZONS. 21 



Characteristic of the region of the Alps durin^^ elevation are the 

 marine, brackish and freshwater molasses, that is, calcareous or 

 argillaceous rocks easy to work, mingled with conglomerates 

 called iiagclfluli a littoral formation. These were produced in 

 Switzerland on the shores of islands during oscillation periods. 



IV. OLIGOCENE OF EUROPE 



This Period is actually well defined in its geographical features, 

 as well as in its fauna and flora ; in France it begins typically 

 with the Ronzon fauna which contains a number of entirely neio 

 types, and it terminates with that of St. Girand le Puy. Some 

 authors, however, Lydekker ('96, p. 191), Lepsius ('92, p. 550), 

 include within the lower Oligocene the Ligurien or Gypse ; this 

 is a cause of great confusion in the literature. 



The duration of the Oligocene may be estimated by deposits 

 in Italy of 2900 metres in thickness. 



Earth Movements. — According to Lapparext ('85, p. 1 164) 

 the Oligocene of Europe begins with the main elevation of the 

 Pyrenees and is marked toward the close by the initial elevation 

 of the Alps. Its first or early earth movements [Etages Infra 

 Tongrien and Stanipien) caused a recession of the sea at the 

 south, and an invasion of the sea from the north — this invasion 

 reached the centre of France ; in the Rhine valley it extended 

 as far south as Basle. The climate during this period was 

 moderate. The second or Etage Aqiiitanien was one of eleva- 

 tion and strongly contrasted with the preceding by a general 

 recession of the sea ; it instituted a period of great freshwater 

 lakes in France and Southern Europe, varied by lagoons with 

 lignitic deposits. Under more temperate climatic conditions, 

 with considerable moisture, the flora was of Indian and Australian 

 type, the deciduous trees increased in number, but palms still 

 flourished as far north as the Baltic ; the bird life of central 

 France (Allier, Milne-Edwards) Avas similar to that of the 

 lakes of Southern Africa. Along certain lake borders however, 

 in Southern PVance (Aix and Gargas, Sapporta), the heat 

 and drought during the latter part of the summer were extreme. 



