338 



ORDERS OF MAMMALIA. 



by a long diastema. There is no antorbital fossa, siicli as 

 exists in Anchitherium. 



In the Lower Miocene of North America we meet with 

 the genus Mcsohipiyvs, the species of which are about as 

 large as a sheep, but with longer legs. The hind-feet are 

 three-toed, as are the fore-feet also, but the latter possess 

 a " splint-bone " (rudimentary metacarpal) representing the 

 little finger. Two of the prsemolars now entirely resemble 

 the molars. 



In the Upper Miocene of ISTorth America McsoliiiJinis is 

 replaced by Miohippus, the animals comprised in which are 



Fig. 6?j~, — Skek'tuu of tlie foot in various forms belonging to the family of tliB Equidce. 

 A, Foot of Orohippits, Eocene ; b, Foot of Anchitherium, Upper Eocene and Lower Miocene ; 

 c, Foot ot Hippario)i, Upper Miocene and Pliocene ; d, Foot of Horse (Eqims), Pliocene and 

 Recent. The figures indicate the numbers of the digits in the typical five-fingered hand of 

 Mammals. (After Marsh.) 



rather larger than a sheep. This genus is intermediate 

 between Orohipptis and Anchitherium, differing from the 

 former in the fact that there are only three digits to the 

 fore-feet, and from the latter in having no antorbital fossa. 

 All tlie feet are tridactylous, the toes being nearly of equal 

 size ; and the little finger of the hand — functionally de- 

 veloped in Orohippus — -is here represented by a " splint- 

 bone." 



Allied to the preceding is the genus Anchitherium , of the 

 European Miocene, in which the species were about as big as 

 a sheep. In many points this genus exhibits Palneotheroid 

 characters, so that it is transitional between the Eqvidw and 



