AMBLYPODA. 513 



This heterogeneous list of characters could not define any natural group, 

 as many of them are of not more than generic or family value.* Several 

 of the most important are not shared by the genus Cori/phodon, a form at 

 that time unknown to Professor Marsh, but which clearly belongs to the 

 same order of Mammalia. My conclusion has been that the Dinocerata do 

 not alone constitute an order of Mammalia, but that they form a division 

 of an order which includes also Cori/pJiodon, and doubtless many other 

 still unknown types, whose position is, as I first stated, between the 

 Prohoscidia and the Perissodactyla, but which has no affinities with the 

 Artiodactyla, as has been asserted. 



Full descriptions of the species and genera of this order first appeared 

 in my essay, "On the Short-footed Ungulata of Wyoming", above quoted 

 (published March 14, 1873). I there described the existence of five toes 

 in the pes of the genus Eohasileus, and the co-ordinal relations of Corypho- 

 don (Bathmodon). In a note published by Professor Marsh, October, 1873, 

 that author asserts that the Dinocerata have "but four toes in the pes"; but 

 in a paper on Uintatherium (JDinoceras), which subsequently appeared, he 

 admits that that genus has five toes in the pes (Am. Jour. Sci. and Arts, 

 Feb., 1876). We owe to later observations of Professor Marsh two of the 

 most important points in the structure of the Dinocerata, viz, the supei-ficial 

 structure of the brain, and the arrangement of the bones of the carpus. 

 He shows {I. c, July, 1874, and February, 1876) that the cerebral hemi- 

 spheres are so small as not to cover any part of the olfactory lobes and the 

 cerebellum; that their surface was nearly smooth, and that their combined 

 diameter was less than that of some parts of the neural canal of the vertebral 

 column. The brain is relatively the smallest among known Mammalia, and 

 resembles strongly that of the Creodont Arctocyon of the French Eocene, 

 figured by Professor Gervais, in the "Archives du Museum", 1870. I sub- 

 sequently showedf that the brain of Coryplwdon presents similar characters. 



The structure of the carpus of Uintatherium, described by Marsh {I. c, 

 February, 1876), is essentially identical with that of Coryphodon, which I 



* As I pointed out in an article in the American Naturalist, May, 1873. 



t My description of the brain of Coryphodon appeared in the Proceedings of the American Philo- 

 sophical Society for March, 1877, and was published April 25th. Professor Marsh's description appeared 

 in the July number of the American Journal of Science and Arts for July, 1877, which appeared near 

 the middle of Jane. 

 33 C 



