J. L. Wortman — Cope's Tertiary Vertebrata. 297 



the rich fauna of the Eocene as heretofore understood, the dis- 

 covery of the Puerco constitutes a bold advance. 



As regards the important additions to our knowledge of 

 special groups, which this work contains, they are so numer- 

 ous that it is impossible to mention more than a few of the 

 leading ones in this connection. We have here presented for 

 the first time any thing like a broad and comprehensive gene- 

 ralization of the" relationships of the hoofed Mammalia. Assum- 

 ing as a basis of understanding the fact that the limb structure 

 has been all important to these animals in the struggle to sur- 

 vive, Professor Cope has divided them into four groups accord- 

 ing to the degree of modification of the carpal and tarsal 

 articulations. 



He has shown that in all primitive ungulates the carpal and 

 tarsal bones are serially arranged ; that is to say, those of the 

 proximal row are directly superimposed upon the correspond- 

 ing elements of the distal set, a condition whose mechanical 

 advantage in sustaining the weight of a bulky body in rapid 

 movement, is much inferior to that of the higher types in 

 which the carpal and tarsal bones interlock. 



The four orders which he thus constructs are the Taxeopoda, 

 Amblypoda, Proboscidea and Diplarthra. The first of these is 

 the most primitive, being pentedactyle, probably semi-planti- 

 grade, bunodont, and in many ways approaching the clawed 

 orders. It attained its greatest development in the Puerco 

 epoch, where it is represented by numerous species and genera. 

 According to the views of Professor Cope, which seem to be 

 unusually well-founded, this group forms the central stem from 

 which the others have been derived, having as a cotemporary 

 in the Puerco horizon the Taligrada, a sub-order, which estab- 

 lishes a close connection between it and the Pantodonta of the 

 later Eocene. 



It is here also that the Hyrax, that anomalous nondescript, 

 for the first time finds fellowship, being at the same time the 

 only living representative of this remarkable' order. It appears 

 to be an oversight on the part of Professor Cope that he did 

 not detect the ancestral connections of the tree Hyrax with his 

 Meniscotheriidaz, a family of the Taxeopoda. It is likewise some- 

 what questionable whether he is correct in giving the Toxo- 

 dontia a position in this order. 



With reference to the immediate connections between the 

 Diplarthra, a group corresponding to the Ungulata of most 

 authors, and the Taxeopoda, comparatively little has been 

 made out; neither do we receive any additional light upon the 

 direct ancestry of the Proboscidians in the present contribu- 

 tion. The internal arrangement of the Taxeopoda is thoroughly 



Am. Jottb. Sci.— Third Seeies, Vol. XXX, No. 178.— Oct., 1885. 

 19 



