71 



branches to one another, and their probable lengths and 

 directions, are still very obscure. 



The second main branch of the higher Mammalia pro- 

 bably split far back into the ancestral forms of two great 

 groups — the first of which became evolved into the Cheirop- 

 tera, the Insectivora, and the Carnivora ; while the second 

 was the stock from which the Prosimiae and the Primates 

 have descended. 



In the first of these series, the extinct Creodontia 

 probably represent the early ancestral Carnivora, from 

 which the Insectivora diverged. The Cheiroptera agree 

 with the Insectivora, and with the primitive Carnivora in 

 many respects. Possibly they may have arisen as a side 

 branch from the Insectivora, and not from the early common 

 ancestors of Carnivora and Insectivora, as shown in the 

 table. The Cheiroptera have undergone great modification 

 since they diverged, the anterior extremities having become 

 converted into organs of flight. The Bats now existing fall 

 naturally into two main groups, which however have probably 

 had a long common ancestry. 



The Insectivora retain many of the characters of the 

 primitive Carnivora, from which they are descended. They 

 have undergone less modification than either the Cheiroptera 

 or the Carnivora, and some of them probably represent 

 better than any other existing forms the primitive higher 

 Mammal from which all the groups above the Sirenia have 

 been derived. The aberrant genus, Galeopitliecus, is best 

 placed as a side branch from the Insectivora. 



The primitive Carnivora must have divided into two 

 ancestral series, the one leading to the Carnivora proper 

 (Fissipedia), while the other diverged to the Seals and their 

 allies (Pinnipedia). The Fissipedia are probably the most 

 direct descendants known of the ancestral Carnivora. They 

 have undergone a considerable amount of evolution, and have 



