330 NATURAL SCIENCE [May 



It is harmless, exhibits a ridiculously small brain-cavity, and has a 

 complete series of teeth adapted for feeding upon succulent vege- 

 tation. With the hoofed mammals, there are also the primitive 

 smooth-brained tiesh-eaters again, or Creodonta, as they are termed. 

 There are likewise true rodents and undoubted examples of lemurs. 



In the next, or Middle Eocene period, the lowly organised but 

 overgrown Amblypoda seem to have become extinct in Europe ; but 

 they have assumed still larger proportions and fantastic shapes in 

 North America. Here, at any rate in a limited area, they are now 

 terribly horned animals, or Dinocerata, with three pairs of bony 

 bosses on the top of the head, and a great pair of tusks hanging 

 downwards from the upper jaw. They seem to have reached the 

 maximum development for animals with such small brain-capacity, so 

 they immediately become extinct. The true odd-toed and even-toed 

 hoofed animals in which the brain gradually enlarges and begins to 

 show complications, are much more flourishing and quite a con- 

 spicuous race. In North America, indeed, one family (Titano- 

 theriidae) arises and soon includes animals as large as small elephants. 

 The Creodonta are also more varied than before, and flying mammals 

 or bats are now completely formed. 



The Upper Eocene fauna is still more advanced, and the 

 differences between the mammals of the Old and New Worlds 

 begin to be more and more marked. The Creodonta are now 

 of less importance than before, and true Carnivora much like 

 modern dogs are met with for the first time at least in Europe 

 {Cynodictis). The ancestral hoofed animals, or Condylarthra, are 

 also few. The odd-toed lioofed animals, or Perissodactyla, are 

 still numerous, and the most important new form is Falacotherium 

 in Europe ; but the Artiodactyla attain the most remarkable de- 

 velopment both in Europe and North America. On the former 

 continent there are the pig-like Choeropotamus, and the primitive fore- 

 runners of the ruminants, Hyopotamus (Ancodus) and Xijyhodon ; 

 while a remarkable short-lived family exhibiting three-toed spreading 

 feet is represented by Anoplothernim and Diplohune. In America 

 there are the Oreodonts (Frotorcodon) and primitive camels {Lepto- 

 tragulus), which must have been still more nearly ruminants. 

 The Rodentia are now very numerous and varied ; on the other 

 hand lemurs appear for the last time on both continents. The 

 opossums (Didclphys) are still abundant. Marine mammals occur 

 for the first time, the primitive whale, Zeuglodon, being found in 

 Europe, Northern Africa, and North America ; while a single 

 Cetacean vertebra of a more modern type has been discovered 

 in the Upper Eocene of Hampshire. There is also some frag- 

 mentary evidence of Sirenia in northern Italy. 



It must be added that the European Upper Eocene mammalian 



