THE MAMMALIA OF THE DEEP RIVER BEDS. 



Ill 



A. EQUINUM. 



A. ATJKELIANENSE. 



Metacarpal iii, depth of proximal end 023 



Metacarpal ii, length 179 



Metacarpal ii, width of proximal end 010 



Metacarpal ii, depth of proximal end 014 



Metacarpal ii, width of distal end Oil 



Metacarpal ii, depth of distal end 020 



Metacarpal iv, length , 177 



Metacarpal iv, width of proximal end 011 



Metacarpal iv, depth of proximal end 014 



Metacarpal iv, width of distal end 012 



Metacarpal iv, depth of distal end 020 



First phalanx of median digit, length 040 



First phalanx of median digit, width of proximal end 033 



First phalanx of median digit, width of middle 027 



First phalanx of median digit, width of distal end 026 



Third phalanx of median digit, length 043 



Third phalanx of median digit, width of proximal end 033 



Third phalanx of median digit, maximum width 046 



First phalanx of lateral digit, length 026 



Second phalanx of lateral digit, length 015 



Third phalanx of lateral digit, length (plantar border) 042 



028 



027 



041 



0285 



044 



027 



016 



028 



The Systematic Position of Anchifherium. 



The relation of Ancliitlierium to the other genera of the equine phylum is a 

 problem of more than ordinary interest, for if we can once establish its s} 7 stematic 

 position with reasonable probability, we shall find that the inferences which may be 

 drawn from the facts have a very important bearing upon many of the open ques- 

 tions as to the mode in which transformation may operate in a given case. The 

 European palaeontologists have very generally regarded this genus as ancestral to 

 the modern PJquidce, and many of these authorities have derived Anchitherium from 

 Palceotherium, Paloplotlierium, or some similar type. Had the wonderful series of 

 American equines never been discovered, it is highly probable that this result would 

 not have been disturbed, though in the light of present knowledge it cannot be 

 accepted. It is not worth while to argue against the derivation of Ancliitlierium from 

 Palceotherium or an allied genus, for since Marsh directed attention to the equine 

 nature of the Eocene Hyracotherium and its allies, the older hypothesis has been 

 almost entirely abandoned, but the position of the genus before us with reference to 

 the existing Equidce and to preceding genera is a much more difficult and obscure 

 problem, more especially since it involves the supposed dual origin and parallel lines 

 of horses in the Old World and the 'New. 



A. P. S. — VOL. XVIII. O. 



