1898] MAMMALIA IN EUIiOFE AND NORTH AMERICA 331 



fauna is best represented in certain phospl)ate-l)earing earths or 

 phosphorites filling an extensive series of fissures in tlie district of 

 Quercy, between Villefranche and Montauban, in the south of 

 l^rance. These fissures, however, were evidently open and l^eing 

 filled with earth and bones long after the close of the Eocene 

 period, so that two or more successive faunas are mixed together, 

 and it is not possible to determine with certainty the age of any 

 particular fossil found in this anomalous deposit. A similar mixture 

 of Eocene and Miocene mammalian fossils, though of a more frag- 

 mentary character, also occurs in several fissure-accumulations of 

 iron-ore (the so-called bohnerz) in Switzerland (as at Egerkingen), 

 in Wiirtemberg (as at Frohnstetten), and in Bavaria (as at 

 Pappenheim). 



Miocene 



Between the Eocene and Miocene strata of Europe, stratigraphical 

 geologists who base their conclusions on the marine deposits, recognise 

 an intermediate formation termed Oligocene. So far as tlie verte- 

 brate faunas are concerned, however, it does not seem possible to 

 admit this division, and the so-called Lower Oligocene falls more 

 naturally into the Upper Eocene, while the Upper Oligocene may be 

 included in the Lower Miocene. 



Adopting this arrangement, the Lower Miocene vertebrate fauna 

 of Europe occurs in the Hempstead Beds which directly overlie the 

 Upper Eocene in the Isle of Wight ; in the lacusti'ine marl of 

 Eonzon, near Puy-en-Velay, and of other districts in southern 

 France ; in other freshwater deposits near St Gerand-le-Puy, Allier ; 

 in the lignites of Rott, near Bonn, of La Rochette, near Lausanne, 

 and of Cadibona, in Liguria ; in the marine Eupelian formation of 

 Belgium ; in marine, brackish-water, and freshwater deposits in the 

 neighbourhood of Mayence ; and in other freshwater formations near 

 Ulm, Wiirtemberg. A corresponding mammalian fauna in ISTorth 

 America occurs in the White River Formation, which was deposited 

 in an extensive series of lakes spread over Nebraska, Dakota, 

 Colorado, Wyoming, and part of southern Canada. The Creodonta 

 are now found for the last time both in Europe and North America, 

 and seem to be represented only by one highly specialised genus, 

 Hyaenodon. The true Carnivora are abundant and varied, including 

 even a cat {Eusmilus) on both continents ; but the viverroids are 

 confined to Europe. Among hoofed animals the Perissodactyla 

 include hornless rhinoceroses on both continents ; while there is a 

 considerable advance in the line of the horses in North America, 

 and Titanothermm represents the highest and last development of 

 the peculiarly American family of Titanotheriidae. Some of the 

 primitive Artiodactyla attain a large size and become of importance, 



