LOZ PRIMITIVE UNGULATA CHAP. 
possess of earher mammals, we must arrive at the general con- 
clusion that two of the existing larger groups of the Eutherian, 
non-Marsupial, mammals were differentiated at quite the begin- 
ning of the Eocene, and were represented by forms from which 
it is possible to derive at least the existing Carnivora, Insectivora, 
Artiodactyla, and Perissodactyla. These were the Creodonta and 
the Ungulate Condylarthra. In addition to these we may 
enumerate as very early types the Lemuroidea, represented by 
such forms as /ndrodon in the New World, and (though later) by 
Necrolemur, ete., in the Old World, and the Edentata, if we are 
to allow as their ancestors the Ganodonta. 
The early Eocene strata also contain representatives of at 
least one order, the Amblypoda, which increased subsequently, 
but has died out without descendants, unless we are to believe 
with some that the Elephants are to be derived from these 
Eocene “ pachyderms.” In later Eocene times the great majority 
of the existing orders, and even subdivisions of orders, are to be 
met with; and there are in addition such totally extinct orders 
as the Typotheria, Ancylopoda, and Tillodontia. Coupled with 
this gradual specialisation in the orders of Eutherian mammals, 
there is naturally a vast increase in the number of generic and 
family types. This culminates perhaps in the Miocene, from 
which time there has been a gradual decline in mammalian 
variety, so that it is justly said that we live now in an epoch 
which is impoverished of mammals. This gradual decay has 
persisted until to-day, as is witnessed by the extinction of the 
Rhytina and the Quagga, and the growing rarity of the White 
Rhinoceros and the American Bison. 
The early Eutherian stock consisted of small mammals 
with small heads and slender, long tails. The limbs were 
pentadactyle, ensheathed in claws or broader hoofs. The fore- 
limbs may have been partly prehensile. The teeth were forty- 
four, completely differentiated into incisors, canines, molars, and 
premolars; and there appears to have been a complete diphy- 
odontism. The canines were not greatly enlarged, and no 
diastema separated any of the teeth. The molars were bunodont 
or of a more cutting pattern, with some five or six tubercles. 
These animals were, moreover, very small-brained. This early 
stock is represented by Creodont and Condylarthrous animals, 
the exact boundaries between which are hardly marked in the 
