94 The Badland Formations of tho Black Hills Region 



ence of five toes on the front foot and four on the hind foot, 

 and there is good reason for believing that at some still earlier 

 stage the pentadactyl nature was complete. In connection with 

 the progressive enlargement of the middle toe, profound altera- 

 tion also took place in other parts of the anatomy, particularly 

 the lengthening of the jaws, increasing complexity of the teeth, 

 pronounced elongation of the lower part of the limbs, degenera- 

 tion of the ulna and fibula, et cetera. 



The phylogeny of the horse was first suggested by the 

 great French paleontologist, Cuvier. The earliest attempt at 

 its expression was made by Kowalevsky, the Russian. He was 

 followed in successive order by Huxley of England, Marsh, 

 Cope, Wortman and Scott of America, and Schlosser of Ger- 

 many, and more recently by Osborn and others. Interpretation 

 by the earlier men showed inconsistencies and omissions, but with 

 increasing collections of well-preserved material it has been 

 possible to eliminate aberrant forms and to add needful material, 

 until now the genealogical series is fairly complete.* For a 

 diagrammatic representation of the more important evolutionary 

 changes see Plate 34 from Matthew. Brief reference is made 

 below to some features of relationship among various members 

 of the family, but the reader desiring to pursue the subject 

 farther, is referred to the papers listed herewith and in the bibli- 

 ography inserted near the end of this bulletin. 



Fortunately the fossils representing the extinct horses are 

 abundant and often well preserved. For some years the Pea- 

 body Museum of Yale University excelled all others in the ex- 

 tent and importance of its collections, but more recently the 



*T!he following recent summary article© are among the best that 



'have been written on the subject. The non-technical ones are readily 



accessible to many readers and all will be found particularly helpful: 



1902. Lucas, F. A. The Ancestry of the Horse. In Animals of the 



Past, 'pp. 159-176, earlier published in MicClure'is Magazine 



(19 00). 



1904. Osborn, H; P. The Evolution of the Horse in America. Cen- 



tury Magazine, Vol. 69, ipp, 3-17. 



1905. Matthew, W. D. The Evolution of the Horse. Am. Mus. Journ- 



al, Vol. 3, Supplement. Guide Leaflet No. 9, (second edition), 



pp. 1-30. 

 1907. Lull, R. S. The Evolution of the Horse Family, as Illustrated 



in the Yale Collections. Am. Journ. Sei., Vol. 23, pp. 161- 



182. 

 1907. Gidley, J. W. Revision of the Miocene and Pliocene Equidae 



off North America. Bull. Am. M'uis. Nat. Hist., Vol. 23, pp. 



865-934. 

 19 08. Granger, Walter. A Revision of the American Eocene Horses. 



Bull. Am. Mus. Nat. Hist., Vol. 2 4, pip. 221-2 64. 



