In Post-pliocene deposits in Siberia, remains of _Rytina_ have been found; while several species of the extinct genus _Halitherium_, perhaps intermediate between _Manatus_ and _Halicore_, have been found in the older Pliocene and Upper Miocene of France and Germany. _Order VII.--UNGULATA._ FAMILY 43.--EQUIDÆ. (1 Genus, 8 Species.) GENERAL DISTRIBUTION. __________________________________/\__________________________________ / \ NEOTROPICAL| NEARCTIC |PALÆARCTIC | ETHIOPIAN | ORIENTAL | AUSTRALIAN SUB-REGIONS|SUB-REGIONS|SUB-REGIONS|SUB-REGIONS|SUB-REGIONS|SUB-REGIONS. -----------+-----------+-----------+-----------+-----------+------------ LIVING SPECIES. | | | | | -- -- -- --|-- -- -- --|-- 2. 3 -- |1. 2. 3 -- |-- -- -- --|-- -- -- -- | | | | | EXTINCT SPECIES. | | | | | 1. 2 -- -- |1. 2. 3 -- |1. 2. 3. 4 |-- -- -- --| 1 -- 3 -- |-- -- -- -- | | | | | The Horses, Asses, and Zebras form a highly specialized group now confined to the Ethiopian and Palæarctic regions, but during the middle and later tertiaries having a very extensive range. The zebras (3 species) inhabit the greater part of the Ethiopian region, while the asses (4 species) are characteristic of the deserts of the Palæarctic region from North Africa and Syria to Western India, Mongolia, and Manchuria. The domestic horse is not known in a wild state, but its remains are found in recent deposits from Britain to the Altai Mountains, so that its disappearance is probably due to human agency. _Extinct Equidæ._--Extinct forms of this family are very numerous. The genus _Equus_ occurs in Post-pliocene and Pliocene deposits in Europe, North America, and South America. In North America the species are most numerous. An allied genus _Hipparion_, having rudimentary lateral toes, is represented {212}by several species in the Pliocene of North America, while in Europe it occurs both in the Older Pliocene and Upper Miocene. Various other allied forms, in which the lateral toes are more and more developed, and most of which are now classed in a distinct family, Anchitheridæ, range back through the Miocene to the Eocene period. A sufficient account of these has already been given in vol. i. chap. vi. p. 135, to which the reader is referred for the supposed origin and migrations of the horse. Family 44--TAPIRIDÆ. (2 Genera? 6 Species.)