422 THE SUCCESSION OF THE VERTEBRATE FAUNAS. 



earths or phosphorites filling an extensive series of fissures in 

 the district of Quercy, between Villefranche and Montauban 

 in the south of France. These fissures, however, were evidently 

 open and being 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 fragmentary character, also occurs in several 

 fissure-accumulations of iron-ore (the so-called bohnerz) in 

 Switzerland (as at Egerkingen), in Wurtemberg (as at Frohn- 

 stetten), and in Bavaria (as at Pappenheim). 



Miocene. 



Between the Eocene and Miocene strata of Europe, strati- 

 graphical geologists who base their conclusions on the marine 

 deposits, recognise an intermediate formation termed Oligocene. 

 So far as the vertebrate 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 lacus- 

 trine marl of Ronzon 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 Rupelian formation of Belgium ; in marine, brackish- 

 water, and freshwater deposits in the neighbourhood of Mayence; 

 and in other freshwater formations near Ulm, Wurtemberg. 

 A corresponding mammalian fauna in North 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 specialized 



