288 



THE AGE OF MAMMALS 



canids, represented by Cynodesmus, are abundant and varied. This is 

 the first geological appearance of the characteristically American family 

 of raccoons, or procyonids, here represented by Phlaocyon. The Mustelidae 

 are represented by the Oligocene Oligobunis and two new forms of superior 

 size {^lurocyon and Megalidis); the latter (M. ferox) is a very powerful 

 mustelid, intermediate in character between the ratel {Mellivora) of Africa 

 and India and the wolverine (Gulo), an animal which subsequently becomes 

 Holarctic in distribution. 



It is striking that every representative of the Testudinata found in the 

 Arikaree, or ' Upper Harrison ' beds is an upland form, and so far as kno\Mi 

 all remains belong to the genus Testudo, which embraces the land tortoises, 

 represented by five species. This is suggestive of the seolian deposition of 

 these beds.^ 



Middle Miocene 



Ticholeptus Zone 



Deep River and Flint Creek, Montana; Mascall, Oregon; Pawnee CreeJc, 

 Colorado. — In the above-named formations of Montana, Oregon, and Colo- 

 rado, which are broadly 

 united as the Middle 

 Miocene or Ticholeptus 

 Zone, we meet another 

 very profound change 

 in the mammalian life 

 of North America, which 

 corresponds to that oc- 

 curring in the Lower 

 Miocene of Europe, 

 namely, the first appear- 

 ance both of the African 

 mastodons and of the 

 short-limbed rhinoce- 

 roses, or TeleoceriniE. 

 It is supposed that these 

 Lower Miocene invaders 

 of Europe reached 

 America in the Middle 

 Miocene, but it is quite possible that future discovery may give a greater 

 age to these formations. Another resemblance to the Lower Miocene of 

 Europe is the occurrence at this level of the earliest horned or antlered 

 ruminants. These, however, have no known European affinities, since they 



1 Loomis, F. B., Turtles from the Upper Harrison Beds. Amer. Jour. Sci., Vol. XXVIII, 

 no. 163, July, 1909, pp. 17-26. 



Fig. 142. — Skull of the typical Middle Miocene oreodont 

 Ticholeptus breviceps Douglass (Type), about |. After Doug- 

 lass. 



