Prof. K. A. von Zittel—On the Mammalia. 461 
Palgocherus and Dremotherium, and in the springing up of a con- 
siderable number of new genera, as Tapirus, Diceratherium, Amphi- 
tragulus, Steneofiber, Titanomys, Hrinaceus, Dimylus, Amphicyon, 
Potamotherium, Herpestes, Proclurus, and others, depend the differ- 
ences between the Upper Eocene, the Oligocene and the Lower 
Miocene faunas of Europe. Amongst the new genera there is, 
further, no single form for which a corresponding related form could 
not be found in the Hocene; only in the modification, differentiation 
and improvement of the older types is the new fauna distinguished 
from the earlier one. With the exception of some Marsupials, 
Rodents, Insectivora and Bats (Didelphys, Myoxus, Cricetodon, Sper- 
mophilus, Sciurus, Talpa, Myogale, Sorex, Hrinaceus, Vespertilio), all 
the larger genera are extinct. 
The rich mammalian fauna of the so-called White-River beds, 
which in North Nebraska, Dakota, Colorado, Wyoming and South 
Canada cover a very extended area, and reach a thickness of from 
40—60 métres, holds an altogether similar relationship to the 
Bridger and Uinta fauna, as the fauna of the Lower Miocene of 
Europe to that of the Upper Eocene and Oligocene. The powerful 
Amblypoda and the peculiar Tillodontia are extinct, the Creodontia 
are shrunk up to a single genus (Hyenodon); the Prosimiz are, 
however, still represented by two genera. For the rest, the White- 
River fauna consists of Marsupials, Perissodactyla, Artiodactyla, 
Rodents, Insectivora, Bats, and genuine Carnivora, and the following 
genera are present in it :'— 
MARSUPIALIA. ARTIODACTYLA. INSECTIVORA. 
Didelphys. *t?Ancodus (E.) tlctops. 
*fElotherium (E.) *f Leptictis. 
\ PERISSODACTYLA. *Y Percherus. *+ Mesodectes. 
{Mesohippus. *1 Leptocherus. *t Geolabis. 
*> Tapiravus. * Acriocherus. 
_ eee (E.) *+Oreodon. CHIROPTERA. 
+Hyracodon. */Poébrotherium. *t Domnina. 
*t Metamynodon. *? Gomphotherium. 
*/Titanotherium. *+Leptomeryx. CREODONTIA. 
( Diconodon. *+ Hy pisodus. *Hyznodon (E.) 
Brontops. *t Hypertraculus. 
Brontotherium. *+ Protoceras. CARNIVORA VERA. 
Menops. (Fissipedia. ) 
Symborodon. RODENTIA. *+Dapheenos, 
Megacerops *Ischiromys. *Galecynus. 
Titanops. *Steneofiber (E.) *Hoplophoneus. 
Allops. “+ Heliscomys. *fDinictis. 
Dalodon. *+Gymnoptychus. 
\ Zeleodus. *;Eumys. PRIMATES. 
*PPaleolagus. *t Laopithecus. 
*t Menotherium. 
Amongst the Perissodactyla, Mesohippus represents only a some- 
what more advanced stage of differentiation of Epihippus, and exactly 
in the same manner Tapiravus is related to Helaletes, Hyracodon to 
Hyrachyus, Metamynodon to Amynodon. 'The Titanotheride, with an 
1 The genera to which the letter (E.) is affixed occur also in the Miocene of Europe. 
For the other marks see the note on p. 460. 
