SUBORDER C 



PERISSODACTYLA 



151 



in flat distally expanded ungual phalanges. > The third trochanter arises 



somewhat above the mid-length of the 

 femur, and forms a prominent ridge. 

 The three cuneiforms are well developed. 

 Falaeotherium is the dominant form 

 in the Upper Eocene deposits of France, 

 England, southern Germany and Switzer- 

 land, and represents the most abundant 

 and characteristic mammalian genus of 

 this horizon. The Paris gypsum has 

 yielded entire skeletons of P. magnum, 

 medium, and crassum Cuvier, while crushed 

 skulls, teeth without number, and isolated 

 bones have been obtained from the 

 lignitic marl of Debruge, near Apt, 

 Vaucluse, as well as from the Phos- 

 phorites of Quercy and the Bohnerz 

 of the Swabian and 

 Franconian Alps. The 

 largest species, P. 

 magnum, attained the 

 dimensions of a 

 rhinoceros ; the small- 

 est, P. curtum, at 

 least that of a pig. 

 Middle Eocene. P. 

 castrense Nouel ; P. 



eocaenum Gervais ; P. rUtimeyeri Stehlin, in part still with simple premolars. 



Fig. 203. 



Palaeotherium crassum Cuvier. Upper Eocene 

 (Lignite), Debruge. Palatal aspect of skull, show- 

 ing dentition. 1/2. 



Fig. 204. 



Palaeotherium crassum 

 Cuvier. First lower 

 molar, l/j. 



Subfamily 3. Anchitheriinae Leidy 



Orbits open posteriorly or incompletely surrounded by bone. Cheek teeth brachy- 

 odont. The two or three posterior premolars molariform, rarely all simple. Superior 

 molars with ^-shaped 

 edolophand two oblique 

 transverse crests and 

 hypostyle. The con- 

 tiguous internal cusps 

 of the crescents of the 

 inferior cheek teeth 

 form two small cones. 

 Lower M^ with a 

 small talonid. Radius 

 and ulna usually dis- 

 tinct. Extremities 

 slender, tridactyl, 

 the lateral digits reaching the ground, and much less robust than the middle one. 



Mesohippus Marsh (Figs. 205, 206). Incisors chisel-shaped, without pits. 

 With the exception of the most anterior, cheek teeth homoeodont. Superior 



Fig. 205. 



Mesohippus hairdi T.eidy sp. Oligocene (White River beds), Dakota. 

 Upper and lower cheek teeth. Vl- (After Osborn.) 



