LÖNNBERG, MAMMALS FROM BRIT. E. AFRICA. 23 



bers of the present fauna of these mountain-forests have lå- 

 ter on become isolatad to their abode when the climate 

 changed and became more dry so that the forests, formerly 

 also covering the plains, by and by dvvindled away and 

 disappeared. The isolation thus effected promoted the chan- 

 ces for the development of new forms in a similar way as 

 sketched above. The Dendrohyrax to be described below is 

 to be understood as a species created by such isolation. 



As the Dendrohyraxes with regard to their brachyodont 

 teeth represent an earlier stage of developement than at 

 least the most typical members of Procavia proper, which 

 have large and hypsodont teeth, it appears rather probable 

 that the former are the more primitive forms, and that the 

 arboreal life is to the Hyracoidea the original life. With 

 other words it means that they became Hyraxes by acquir- 

 ing the faculty of climbing and by adapting themselves to 

 the arboreal life. The life on and among rocks should thus 

 be secondary. I think this proceeding could be explained 

 in the following way. Originally the greater part of Africa 

 was covered with forests. For such a theory speaks strongly 

 the fact that members of the in present time chiefly »west- 

 ern» forest fauna are to be found far to the east in quite 

 isolated forests, to which they impossibly had been able to 

 spread under the now prevailing conditions, and they are 

 thus relicts. All Tree-Hyraxes in isolated forests in the east 

 are such relicts. But when the climate changed so that the 

 forests, originally continuously covering the whole country, 

 died away except on the mountains and some other places 

 with sufficient moisture, so that the land between these iso- 

 lated forests gradually changed into steppe and thornbush, 

 the conditons of life for the Hyraxes became very different. 

 Some of them adapted themselves gradually to live among 

 rocks and use the crevices and cracks in them as places of 

 refuge instead of the hollow trees which had served their 

 ancestors. By and by they also had to adapt themselves 

 by force of circumstances to feed on coarser plants and 

 grass instead of the diet of tender leaves and fruits of the 

 forest trees which suits the Tree-Hyrax. In connection with 

 increased wearing of the teeth caused by the coarser diet 

 they developed hypsodont teeth just as has been the case 

 under similar conditions with many Ungulata. They became 



