PERISSODACTYLA. 



59' 



Pliocene of Amer. Hipparion * Christol., grinding teeth less hypsodont 

 than in Equus (half the length), anterior inner tubercle of upper molar 

 isolated and laminae of enamel 

 more plicated than in Equus ; foot 

 tridactyle, outer digits not reaching 

 ground, ulna rather better de- 

 veloped than in the horse, about 

 the size of a donkey ; U. Miocene 

 and Pliocene of Eur., N. Amer., 

 and Asia. 



Fam. 3. Palaeotheriidae. Orbits 

 not closed, grinding teeth brachy- 

 odont, rooted, valleys not filled 

 with cement ; hinder premolars 

 usually like the molars, rarely 

 simpler ; last lower molar with or 

 without a third lobe ; u. grinders 

 with W-shaped outer wall ; 1. 

 grinders with two crescents which 

 at their point of union form one or 

 two small cusps ; radius and ulna 

 separate ; feet tridactyle, metapodia 

 relatively short, the lateral digits 

 reaching the ground ; U. Eocene and 

 Miocene of Eur. and N. Amer. 

 Palaeotherium G. Cuv., u. grinders 



■-<^. 



Fig. 313. — A liaif Willi i'-.i i-larof 

 Palaeotherium magnum (alter Owen, 

 from Flower and Lydekker). //con- 

 cavities of outer wall, (» postero-exter- 

 nal tubercle (metacone), ft antcro- 

 external tubercle (paracone), c postero- 

 internal tubercle (hypocone), forming 

 with the intermediate tubercle which 

 is not distinct the posterior transverse 

 ridge, d antero-internal tubercle 

 (protocone) forming with the not 

 distinct antero-intermediate tubercle 

 i (protoconule) the anterior transverse 

 ridge, e median valley, g posterior 

 valley. 



with W-shaped outer wall and two 



oblique transverse ridges (Fig. 313), the intermediate and inner tubercles 

 forming the transverse ridges and not distinct from each other ; in the 

 lower molars the outer tubercles are crescentic and convex outwards (Fig. 

 314), but the inner tubercles (pillars of the horse) are not distinct; the 

 three cuneiforms of the tarsus (Fig. 316, E) are separate ; 

 the skull is rather tapir like, and the neck shorter than 

 in Equidae ; they attain to the size of a rhinoceros ; 

 U. Eocene of Europe. Paloplothermm Ow., the inter- 

 mediate tubercles are distinct in the u. grinders, with 

 cement; pes (Fig. 316, D) as in the last, U. Eocene 

 of Europe. Mesohippus f Marsh, u. grinders with 

 W-shaped outer wall formed of the two V-shaped 

 outer cusps, there are fovir other cusps not vinited, 

 viz. two intermediate and two internal ; a splint like 

 metacarpal 5, in possessing which it approximates to 

 the next family ; Oligocene of N. Amer. Anchitherium % 

 H. v. Meyer (Figs. 315, C, 316, C), more horse-like than 

 the other genera of this family, incisors slightly pitted, 

 u. grinders with W-shaped outer wall ; inner tubercles 

 connected with the outer wall bj^ the semilunar inter- 

 mediate tubercles (the distinction between the inter- 

 mediate tubercles and the inner is not clear, as in 



* Cope, Review of N. Amer. sp. of Hippotherium, Proc. Amer. Phil. 

 Soc, 1889. 



t Osborn and Wortman, Bvll. Amer. Mus. N. Hist., 7, 1895, p. 352. 

 X W. Kowalevsky, 3Iem. Akad. Imp. Sci., Petershourg, (7), 20, 1873. ; 



'IG. 314. — Palaeo- 

 therium crassuni, 

 Cuv., anterior 



lower molar (from 

 Zittel). /3 antero- 

 external tubercle. 

 a antero-internal 

 tubercle not dis- 

 tinct from /3 ; y 

 postero - external , 

 •yi postero-iuter- 

 nal tubercle, ^' 

 cusp formed 



where the cres- 

 cents meet. 



