MAMMALIA, 523 
Pliocene and Upper Miocene ; .4zchétherium, an animal about the size 
of a sheep, with three functional toes (like the rhinoceros), is found in 
the late Miocene; whilst a similar form in the early Miocene shows the 
vestige of the fifth toe as a small metapodial splint-bone. Pachynolophus 
of the Upper Eocene and Ayracotherium of the Lower Eocene were 
still smaller (about the size of a hare), and in the front-limb they had 
four toes (2, 3, 4 and 5) and three on the hind—in fact, resembling in 
this feature the tapirs; one species of Pachynolophus shows a vestige 
of the first digit in the presence of a splint-like metacarpal. These 
types also show the changes in other structural features, such as the 
teeth. (See Fig. 361.) 
In the New World the same series has been made out and carried 
back even further to the little Phesacodus of the Eocene, with five per- 
fect plantigrade digits and a complete dentition, which, with its allies, 
forms a meeting point of the modern Ungulata. 
A very interesting point is the separate series of the New and Old 
World, and it has been maintained with much reason that the horse 
was independently evolved in the two hemispheres. 
In the case of the ox a similar” series can be made out, true Bovide 
dating back to the Upper Miocene, whilst forms allied to the pigs and 
chevrotains go back to the Eocene. On this point we may quole 
Flower and Lyddeker :—‘‘ The primitive Artiodactyles, with the typical 
number (44) of incisor, canine and molar teeth, brachydont molars, 
conical odontoid process, four distinct toes on each foot, with meta- 
podial and all carpal bones distinct, no frontal appendages, and (in all 
probability) simple stomach and diffused placenta, were separated at a 
very early period into Bunodonts and Selenodonts, although there is 
evidence of intermediate forms showing a complete transition from the 
one modification to the other. These and other fossil forms so com- 
pletely connect the four groups-——Suina, Tylopoda, Tragulina and 
Pecora—into which the existing members of the sub-order have become 
divided, that in a general classification embracing both living and ex- 
tinct forms these divisions cannot be maintained.” 
4 and 5.—THE Doc (Canis familiaris) and Cat (felis 
domesticus).—TRANSITION CURSORIAL TYPES. 
The dog and cat are examples of mammals which, whilst 
having fully adopted the quadrupedal terrestrial mode of 
life, have retained the varied use of their limbs in other 
directions to such an extent that these limbs do not show 
complete adaptation to a cursorial habit. 
Both belong to the large and important order of Carn- 
vora, which, in the most typical representatives, feed upon 
the flesh of other mammals. This is usually the case with 
both the dog and cat, but the latter, like the whole 
family of Fedde, is in this respect the most typical of all 
