234 



ANNALS NEW YORK ACADEMY OF SCIENCES 



PEEISSODACTYLA 



The or del Perissodactyla is represented to-day by three widely sepa- 

 rated families — the rhinoceroses, Ethiopian and Oriental ; the tapirs, 

 Neotropical and Oriental, and tlio horses, Asiatic and Ethiopian. The 

 last group is the most progressive and moilernized, but the whole order 

 must be regarded as having seen its best days and as passing towards ex- 

 tinction in competition with the better organized and more adaptable 



FtG. IG. — Dispersal and distribution of the Perissodactyla 



The tapirs are on the whole the most primitive and their i)resent distribution widely 

 discontinuous. The rhinoceroses are less widely dispersed and the horses the most cen- 

 tral in their present distribution. All were inhabitants of Tertiary Holarctica, but their 

 dispersal centers appear to have been Pahearctlc, as indicated. 



Artiodactyla. The geological record affords abundant evidence of the 

 Holarctic origin of all the Perissodactyla. The ancestry of each race can 

 be traced back in the Tertiary faimre of Europe and the United States, 

 in a series of approximately ancestral stages, sometimes closer in one re- 

 gion, sometimes in the other, to a group of closely allied primitive peris- 

 sodactyls in the early Eocene of l)oth countries. In South America, the 

 order is unknown until the late Pliocene and Pleistocene. In other re- 



