CHAP. XVII.] MAMMALIA. 229 



last Catalogue (1873) he divides the genus into three — Hyrax, 

 Euhyrax and Dendrohyrax — the latter consisting of two species 

 confined apparently to West and South Africa. 



No extinct forms of this family have yet been discovered ; the 

 Hyracothermm of the London clay (Lower Eocene) which was 

 supposed to resemble Hyrax, is now believed to be an ancestral 

 type of the Suidse or swine. 



Order X.—RODENTIA. 



Family 55.— MUEID^. (37 Genera, 330 Species.) 

 General Distribution. 



The Muridse, comprising the rats and mice with their allies, are 

 almost universally distributed over the globe (even not reckon- 

 ing the domestic species wdiich have been introduced almost 

 everywhere by man), the exceptions being the three insular 

 groups belonging to the Australian region, from none of which 

 have any species yet been obtained. Before enumerating the 

 genera it will be as well to say a few words on the peculiarities 

 of distribution they present. The true mice, forming the genus 

 Mus, is distributed over the whole of the world except IST. and S. 

 America where not a single indigenous species occurs, being 

 replaced by the genus Hesperomys ; five other genera, compre- 

 hending all the remaining species found in South America are 

 peculiar to the Neotropical region. Three genera are confined to 

 the Palsearctic region, and three others to the Nearctic. No less 

 than twelve genera are exclusively Ethiopian, while only three 

 are exclusively Oriental and three Australian. 



Mus (100-120 sp.) the Eastern Hemisphere, but absent from the 

 Pacific and Austro-Malayan Islands, except Celebes and Papua ; 

 lasiomys (1 sp.) Guinea; Acanthomys (5-Q sp.) Africa, India and 



