CHAPTER XII 



THE ARTIODACTYL UNGULATES 



Ungulates in general — Differences between Artiodactyls and 

 Perissodaetyls — The Pigs and Hippopotamus — Camels and 

 Llamas — Divisions of the Pecora — Deer and Giraffes — 

 The hollow-horned Pecora — Paleontological history of the 

 Artiodactyls. 



THE UNGULATES IN GENERAL 



Hoofed animals or Ungulates are a numerous and very varied 

 throng of Mammals from among which can be separated the 

 even-toed Artiodactyls and the odd-toed Perissodaetyls but 

 there still remain among modern types the Elephants and the 

 Hyrax, the former representing the remnant of a once numer- 

 ous group, the latter a quaint and zoologically isolated form. 



Broadly speaking the distinction of Artiodactyls and Perisso- 

 daetyls as even-toed and odd-toed Ungulates respectively is 

 doubtless good enough but for scientific purposes a more pre- 

 cise definition would be: that whereas, the axis of the foot in 

 the Perissodaetyls passes through the third digit, in the Artio- 

 dactyls it runs between the third and fourth which together 

 form the irreducible minimum. 



But it is not merely in the feet alone that these two groups 

 differ from each other. The skeleton and soft parts of the Perisso- 

 dactyl show significant differences from the corresponding 

 structures in the Artiodactyl and what is more striking the 

 several parts of the body are wonderfully alike within each of 

 these orders although belonging to animals very various in 

 external form. There is not space nor would it be profitable 

 in the present connection to discuss these differences in detail. 



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