558 THE MAMMALIA OF THE UINTA FORMATION. 



by the movement of the navicular above the cuboid. Cope has himself recognized 

 the difficulty arising in the Amblypoda from the union of limited diplarthrism in 

 the carpus with extreme diplarthrism in the tarsus. In Macrauclienia we find a pecu- 

 liar displacement in the carpus and no asti-agalo-cuboidal contact in the tarsus. 



The fibulo-calcancal focet may be regarded as a secondary character, since it is 

 developed independently in so many phyla — as a trochlear joint in Memscotheriwn, 

 Macrauclienia. the Artiodactyla ; as a supporting facet in the Proboscidia, Titano- 

 theridaa and Hyracotheridje. It cannot be employed in ordinal classification [vs. 

 Cope, Tert. Vert., p. 378). 



Third: The definitions based upon the carpal series cannot 

 be availed of strictly as employed b}' Cope.* For (1 ) in some 

 of the Amblypoda (Uintatherium) the scaphoid has a broad postei'ior facet upon the 

 magnum, although of less extent than the lunai' unciform facet. (2) In the Probos- 

 cidia the lunar frequently rests upon the trapezoid, and sometimes upon both the 

 trapezoid and unciform. (3) In Maerauchenia the lunar is entirely excluded from 

 the unciform, the cuneiform resting upon the magnum. 



A comjDarison of the entire evolution of the carpus and of the tarsus shows that the 

 former, while moi'e complex, is subject to more definite laws, and is therefore more 

 available for purposes of classification. The carpal characters are constant and dis- 

 tinctive, but not exactly as interpreted by Prof. Copef — we must look at the manus 

 as a whole, including the metacarpals. The tarsal displacements can be employed for 

 subsidiary definition only. It has thus been shown that Cope's whole system breaks 

 down if Ave attempt to establish a parallel between the evolution of the cai-pus and 

 the tarsus in relation to displacement. 



"With these limitations the })rinciple of classification of the ungulates by foot 

 structure loses the universal application claimed for it by Cope, but is by no 

 means invalidated to the extent held by Riitimeyer.J Giving the first rank to the 

 characters of tlie manus, and second to those of the pes, the folloAving modifi- 



*'lVitiary \'cilclii-.il;i, p. 37G. 



f Tfrliary Vcrtelirnta, p. 377. "In Uie first place I find the diversity in the structure of the carpus to be greater 

 in the relations of the magnum and scaphoidus than in the relations between the unciform and the lunar. In other 

 words the trapezoides and magnum are more variable in their proportions than is the cuneiform. » * » I therefore 

 view the relations of these bones as more characteristic." In the succeeding section, V, this view is .'-liown lobe 

 untenable. 



t Op ciL, p. 18. 



