MOLAR TEETH OF THE MAMMALIA EDUOABILIA. 265 



seen in Hippopotamus in the increase in development of the lat- 

 eral or first and fourth digits, thus equaling the number in the 

 fore-foot of Tapirus and Menodus, though preserving the equal- 

 ity of the two median digits. But an inequality of these digits 

 appears in the genera Anoplotherium and Cmnotlierium, as has 

 been stated^ in the following language : '^In Anoplotherium se- 

 cundarium the digit ii is developed in each foot, though not 

 nearly so long as m, which is nearly symmetrical in itself. There 

 is an approach to the same structure in the manus of Cmnotlie- 

 rium.^^ The only approximation to the Proboscidian type is to be 

 seen in the shortening of the metapodial bones in Hiiopopotamus, 

 a point of very inconsiderable value. 



Perissodadyla. — Approximation to the preceding order is 

 made in the anterior foot of Menodus, in which, according to 

 Marsh, there are four toes of nearly equal size, f Apj^roximation 

 to the Proboscidia X is seen in Symtorodon, where the cuboid facet 

 of the astragalus is rather larger than in Rhinoceros, and devel- 

 oped much as in Bathmodon ; the small third trochanter of the 

 femur is also much like that in Bathmodon. The osseous horn- 

 cores may be compared with those on the front of Loxolophodon. 

 The knee was probably free from the integument of the abdomen, 

 as in Proboscidians, In all other respects there is no approxima- 

 tion to this order. 



Proboscidia. — The approximations to other orders in the 

 structure of the feet are only to be seen in the Eocene genera 

 Bathmodon and Eohasileus. The latter, or its ally JJiyitatherium, 

 presents, according to Marsh, but four toes on the hind foot ; the 

 anterior has five. In the former point we have a resemblance to 

 Hippopotamus, but one of little significance, in view of the radical 

 differences between the two in the form of the astragalus, cal- 

 caneum, and cuboid bones. The former is essentially Proboscidian 

 in all respects, with the addition of a cuboid facet alongside of 

 and behind the navicular, as in Symhorodon ; thus constituting a 

 Perissodactyle character, but leaning to the forms of that order 

 which betray probably the closest, though slight, approach to the 

 omnivorous division of the Artiodactyla. Thus, while the Uinta- 

 theriidcB present the Proboscidian type of feet and molar dentition, 



* Huxley, "Anatomy of the Vertebrated Animals," p. 321. 

 f "American Journal of Science and Arts," 1873, p. 486. 



i This should be Amblypoda, not separated from the Proboscidia at the time 

 this was written. (Ed. 1886.) 



