836 SLO DEES SHMUS SINMCLOIZINILS, 
Rhinoceroses maintained a somewhat uniform structure, both in 
Europe and America, differing, so far as we know, in size rather 
than in proportions. Their dentition and their feeding habits 
were probably similar to those of the 2. dicornis of Africa and 
the A. sondaicus and R. sumatrensis of Asia, namely, upon leaves, 
shrubs, and softer herbage. After the extinction of the rival 
families, however, there was naturally a tendency on the part of 
the true Rhinoceroses to enter the peculiar local habitats pre- 
viously occupied by the Hyracodonts and the Amynodonts, and 
they accordingly diverged into upland and lowland, short and 
long-limbed, brachydont and hypsodont types. 
Geological and geographical distribution—(1) The Hyraco- 
dontidez, including Ayrachyus, Triplopus, and Hlyracodon, are very 
abundant, displaying a great range of size in the Middle Eocene 
and Oligocene of North America, and are possibly represented in 
the Eocene of Europe by species which have been mistakenly 
referred by Rutimeyer and others to Lophiodon. (2) The 
Amynodontide are known from the Upper Eocene or Washakie 
and Uinta Beds of North America, and are also possibly repre- 
sented by species referred to Lophiodon in the Eocene of Europe, 
although it is difficult to determine this from the teeth alone; 
the latest American type is Metamynodon of the Oligocene, but 
Cadurcotherium represents a later and probably final stage of 
development in the Oligocene and Lower Miocene of France. 
(3) The Rhinocerotide are first doubtfully known in the Upper 
Eocene of Europe, then suddenly appear in abundance in the 
Lower Oligocene. They are grouped in four subfamilies. (1) 
Aceratheriine of Europe and America. These hornless types 
ranged through all the Miocene of North America, and then 
apparently became extinct upon this continent, but in Europe 
they extended into the Pliocene, and in Asia into the Middle Plio- 
cene. (2) The Diceratheriine, or pair-horned types, have been 
found only in the Lower and Middle Miocene of North America 
and Europe. (3) The earliest Rhinocerotinz, or Rhinoceroses 
possessing median horns, branched off from the Aceratheres in 
the Middle Miocene of Europe; they divided into three sub- 
