SOME EARLY MAMMALS 249 
have two extra toes fairly well developed, and all nearly of the 
same size. In such cases the result is something very like the 
feet of the ancient American type Protohippus, and the European 
Hipparion. 
We have pointed out previously that the mammals of early 
Tertiary days had small brains, and the oldest ancestors of the 
horse are no exception to the rule. Professor Marsh has clearly 
proved that during this era a gradual increase in the size of 
the brain took place. It is interesting to find that the growth 
was mainly confined to the cerebral hemispheres, or higher 
portion of the brain. In most groups of mammals the brain 
has gradually become more convoluted, and thus increased 
in quality, as well as in quantity. In the long struggle for 
existence during the whole of Tertiary times the big brains won, 
as they do now. Applying this to our ancestral horses, it is easy 
to see that, as they acquired greater speed, and so roamed over 
larger tracts of country, they had to use their brains more. 
We pass on now to give a brief account of a strange elephantine 
creature that lived in Eocene times, both in America and Europe, 
the Coryphodon! (so named from its teeth), a restoration of 
which is seen in Plate XL. The complete skeleton, as restored 
by Professor Marsh, is shown in Fig. 92.2. The history of 
this remarkable animal, so long shrouded in obscurity, is worth 
recording here. The specimen on which the genus was founded 
by Sir R. Owen, in 1846, is unique, and was dredged up 
from the bottom of the sea, between St. Osyth and Harwich, 
and consists of the right branch of the lower jaw. This dis- 
tinguished naturalist confessed that he had seldom felt more 
' Greek —horufé, a ridge ; odous, odontos, tooth. 
* From Professor Marsh’s paper, Amer. Journ. Science, xlvi. (1893), p. 325, 
a copy of which he kindly sent to the author. 
