



IIYRACIIKK 



415 



only be possible here to give details of some of the more interest- 

 ing or best-known forms. 



The characters by which the skeleton of the feet of the Sub- 

 ungulata are distinguished from those of the Uneulata Vera have 

 been already mentioned on p. 275. In addition to these it may 

 be observed that the feet frequently have five functional digits, 

 and may he plantigrade ; while the upper surface of the astragalus 

 is generally flattened, instead of presenting the strongly-marked 

 pulley-like ridges and groove so characteristic of the Ungulata 

 Vera. 



Suborder Hyracoidea. 



Family HyraciD-E. 



This division is constituted to receive a single family of mam- 

 mals, the affinities of which have long constituted a puzzle to 







Fig. 170. —Hyrax capensis. 



zoologists. They were first placed among the Rodents, to which 

 animals their small size and general appearance and habits give 

 them much superficial resemblance. Cuvier's investigations into 

 their anatomical structure, and especially their dental characters, 

 led him to place them among the Ungulates, near the genus 

 Jt'hinoceros, a position long accepted by many zoologists. Further 

 knowledge of their organisation and mode of development caused 

 Milne-Edwards, Huxley, and others to disassociate them from this 

 connection, and, failing to find any agreement with any other known 

 forms, to place them in an order entirely apart. Palaeontology has 

 thrown no light upon the affinities of this anomalous and isolated 

 group, as no extinct animals possessing their distinctive characters 

 have as yet been discovered. 



