EvoiATios OF rill-: noix'si-: is \.\rrh'E 17 



t'oot. l)Ut llu' cciitrMl toe in cmcIi tool is l)('c()miii<>; iimcli l.-ii«i('i- lli;iii llic 

 si(l(> toes. 



Paldotlinium and Pldijiolopfnis of the r|)|)('r lOoccnc ol' lluro|)(' 

 form a side l)raii('li of \\\v horse lin(>. 'I'licy wvvv wvy ahuiidaiit in Iairoj)c. 

 ))Ut hav(^ not Ixhmi found in the New World. One of tlicsc animals was 

 thouiiht l)y Prof(\ssor Huxl(\v to be a direct ancestor of the hoi-se. hut it is 

 now considei'cd to he merely a collateral i'elativ(>. Some sj)ecies of 

 PuUvothvriuni were of larjie size, e(iual to a tapii'. They weic first de- 

 scribed in the year 1804 by the cel(>brat(Ml Baron Cuviei- from remains 

 found in the jrypsuni (iuarri(\s of Montmartre, Paris. 



THREE-TOED HORSES 



5, () and 7. Mesohippus and Miohippus. Oligocexp:. In thi.s 

 stage there are three toes on each foot, and a splint representinj< the fifth 

 digit of the fore foot of the Eocene ancestors. The middle toe is now 

 much larger than the side toes, which bear very little of the weight of the 

 animal. Three of the premolars have now become entirely like the molar 

 teeth, the crests on the crown are completely formed, and the outside 

 crest in the upper molars has taken the shape of two crescents. In the 

 Lower and Middle Oligocene are found several species of Mesohippus 

 mostly of the size of a coyote, represented by two mounted skeletons, and 

 various skulls, jaws and feet. In the Upper Oligocene occurs Miohippus 

 ititermedius as large as a sheep, of which a fine skeleton is exhibited in the 

 pavihon case. Several other species of larger or smaller size are repre- 

 sented by skulls and jaws. 



The series of skeletons in the pavilion case shows in a very striking 

 wa\^ the steady increase in size from the Low^r Eocene to the Upper 

 Oligocene, and the reduction of the side toes with concentration of the 

 weight upon the middle toe. 



Fig. 7. Mesohippus. Middle Oligocene. Ui)i)er teeth, natural size. Short- 

 crowned teeth, no cement, second, third and fourth premolars like molars 



8a. Anchitherium and Hypohippus. ]\Iiocexe. Anchitherium 

 has been found onl}- in Europe, and is still verv incompletely known. It 

 is much, like Mesohippus, but is larger and has the crests of the teeth some- 

 w^hat higher and more complete. Hypohippus is off the direct line of 

 descent; its teeth are like those of Anchitherium, bv which name it has 



