186 
AMBLYPODA. 
(published March 14, 1873). I there described the existence of five toes 
in the pes of the genus JEobasileus, and the co-ordinal relations of Coryplio- 
don {Bathmodon). In a note published by Professor Marsh, October, 1873, 
that author asserts that the JDinocerata have “but four toes in the pes”; but 
in a paper on UintatJierium (Blnoceras), which has recently 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 stmcture of the Binocerata, viz, the superficial 
structure of the brain, and the arrangement of the bones of the carpus. 
He shows {1. 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; and that their combined diameter was less than that of some 
parts of the neural canal of the vertebral column. This information is, 
however, accompanied by serious errors of determination. (See on the 
brain of Corypliodon, below.) The brain is relatively one of 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 show in another place that the brain of 
Coryphodon presents similar characters, and discuss their significance further 
on in reviewing the characters of the Eocene fauna. 
The structure of the carpus of TJintatlierhm^ described by Marsh (1. c., 
February, 1876), is essentially identical with that of Coryphodon, which I 
described in the Systematic Catalogue of the Vertebrata of the Eocene of 
Kew Mexico (April, 1875). 
The Pantodonta are confined, so far as discoveries extend at present, to 
the Lower Eocene or Wasatch beds, in the Rocky Mountain region, while 
the Binocerata are confined to the higher or Bridger Eocene strata. The 
former suborder includes two genera, Coryphodon, Owen, and Metalophodon, 
Cope; the Binocerata also two, Uintatherium, Leidy, and Loxolophodon, 
Cope. 
