GEOLOGICAL HI8T0EY OF HOESE 147 



In a revision of the American Eocene horses, Mr. Granger* 

 distinguishes twenty-six species, all the three genera to which 

 they belong being distinct from the early horses found in 

 Europe. The American Eohippus appears to be closely re- 

 lated to the Old World Hyracotherium, while Epihippus ap- 

 proaches Lophiotherium. We thus have a somewhat parallel 

 series in the two continents. 



In the Oligocene deposits the horses are still small, some 

 of them less than eighteen inches high at the withers. 

 Twenty-eight species, belonging to the two genera Mesohippus 

 and Miohippus, have been described by Professor Osbom.f 

 Sixty more species are mentioned by Mr. Gidleylj: as having 

 been procured in the Miocene and Pliocene beds, and over half 

 a dozen more from Pleistocene strata. Thus we know from 

 America already about one hundred and twenty different kinds 

 of fossil horses. They gradually increase in size as we pro- 

 ceed from the older to the newer deposits. The species with 

 many toes are replaced by others with fewer toes, until we 

 come to the highest form of specialization in the modem 

 horse. All that remains of the outer toes is a splint-bone left 

 on each side of the single toe, while the teeth which originally 

 possessed short crowns have now long ones. There is ap- 

 parently a gradual evolution from smaller and simpler forms 

 to larger and more complex ones, as we glance from the older 

 horse remains to the recent pnes. And yet not a single gradual 

 transition from one genus to the other seems to be known. 

 No wonder that one of our foremost palaeontologists exclaims : 

 " The supposed pedigree of the horse is a deceitful delusion, 

 which simply gives us the general process by which the tri- 

 dactyle foot of an ungulate can be transformed in various 

 groups into a monodactyle foot in view of an adaptation for 

 speed, but this in no way enlightens us on the palaeontological 

 origin of the horse. "§ 



Considering the extraordinary abundance of horse remains 

 in North America, and even in the south of South America, 



* Granger, W., " American Eocene Horses," p. 233. 

 t Osborn, H. P., "New Oligocene Horses." 



% Gridley, J. W., "Miocene and PKocene Horses of North America." 

 § Dep6ret, 0. H., " L'6volution des Mammiferes Tertiaires," OXL., 

 p. 1517. 



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