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 1 (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 E. 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 



1 Greek korufe, a ridge ; odous, odontos, tooth. 



- From Professor Marsh's paper, Amer. Journ. Science, xlvi. (1893), p. 325, 

 a copy of which he kindly seat to the author. 



