2 6 THE POPULAR SCIENCE MONTHLY. 



bones of the horse are in reality the rudiments of the fingers we have 

 represented them to be, and might further demand proof positive of 

 their nature. Fortunately, geology and the science of fossils together 

 come to our aid, with as brilliant a demonstration of the steps and 

 stages of the degradation of the horse's fingers as the most sanguine 

 evolutionist could hope to see. From Mother Earth, whose kindly 

 shelter has sufficed to preserve for us the remains of so many of. the 

 forms of the past, we obtain the means for constructing a genealogical 

 tree of the equine race, by methods of certain kind, and through the 

 exhibition of fossils, each bearing an impress of its history, which, to 

 use Cuvier's expression, " is a surer mark than all those of Zadig." 



Our theoretical journey backward into the ages begins with the 

 Recent or last-formed deposits those which lie nearest the outer sur- 

 face of our earth. The Recent or Quaternary period forms a division 

 of the Tertiary period, that is, the latest of the three great epochs into 

 which, for purposes of classifying fossil forms by their relative ages, 

 the geologist divides the rock-formations. The Tertiary rocks, com- 

 mencing the list, with the last-formed or uppermost strata, begin with 

 the Quaternary or Recent deposits ; next in order succeed the older 

 Pliocene rocks ; then come the Miocene formations, and lastly succeed 

 the Eocene rocks. These last are the oldest of the Tertiary period, 

 and lie in natural order upon the Cretaceous or Chalk Rocks, which 

 themselves belong to an entirely different and anterior (Mesozoic) 

 period in the history of our globe. The first fossil that is, the last- 

 deceased horses we meet with are found in the Quaternary and Plio- 

 cene, or the last-formed deposits of the Tertiary system. Between 

 these earlier Pliocene horses and our own Equidae there are no material 

 differences ; and the limbs of these forms may therefore be diagramma- 

 tized as depicted in Fig. 12, AA 1 ; the cannon-bone in all of these 

 figures being marked a ; the splint-bones dd ; the "pastern" and 

 "coronary" bone b, e, and the "coffin-bone"/. 



But near the beginning; of the Pliocene formations of the Old 

 World, and in the oldest of the Miocene rocks which lie below them, 

 we find a member of the horse famity which differs in certain important 

 respects from the horses of the Recent period, and from those of to-day. 

 The fossil horses alluded to are found not merely in Europe, but in the 

 Sewalik Hills in India, and they must therefore have possessed a very 

 wide range of distribution. When first discovered, M. de Christol called 

 this species of horse Hipparion, a name which has been still retained 

 for it, amid that constant alteration in zoological nomenclature which 

 is the labor of the foolish and the sadness of the wise among us. What 

 are the chief peculiarities of Hipparion ? Briefly stated, in the larger 

 development of the "splint-bones" (Fig. 12, CC), which, according 

 to Owen, must have " dangled by the side of the large and functional 

 hooi (or third toe) like the pair of spurious hoofs behind those forming 

 the cloven foot in the ox." This conformation, continues Owen, " would 



