DINOCERATA, TILLODONTIA, AND TOXODONTIA. 373 



reptilian brain in any known Mammal. In D. mirabile, the 

 entire brain was actually so diminutive that it could appa- 

 rently have been drawn through the neural canal of all 

 the prsesacral vertebrae, certainly through the cervicals and 

 lumbars." 



The head could be lowered to the ground, and though the 

 nasal bones are elongated, there is no evidence of the exist- 

 ence of a proboscis. The limbs are short, the fore-legs shorter 

 than the hind-legs ; and the femur was not provided with a 

 third trochanter. The tail is short and slender, and the ribs 

 are furnished with rudimentary uncinate processes. The feet 

 are furnished with five toes each (fig. 657, B and c), and 

 have a general resemblance to the feet of the Proboscideans. 

 In the hind -foot the hallux seems to have been small or 

 rudimentary. The chief genera included by Marsh among 

 the Dinocerata are Dinoceras, Uintatherium, and Tinoceras, the 

 last being stated to be identical with the Eobasileus and Lox- 

 olophodon of Professor Cope. All the remains of this singular 

 group which have been hitherto brought to light are from 

 the Middle Eocene of North America. 



Oeder VIII. TiLLODONTiA. — This order has been estab- 

 lished by Professor Marsh for the reception of some singular 

 Mammals from the Eocene Tertiary of the United States. 

 The following are the characters of the order, so far as pub- 

 lished : The molar teeth have grinding crowns, as in Ungulates, 

 and may have distinct roots, or may grow from permanent 

 pidps ; small canines are present in hoth jaws ; and each jaw 

 carries two long sccdpriform incisors, resembling those of Ro- 

 dents in form and in growing from persistent pidps. The feet 

 are plantigrade and pentadactyle, and the digits were apparently 

 ^unguicidate. The femur has a third trochanter, and the radius 

 and idna and tibia and fibula are distinct bones. 



The order includes two distinct families — one, the Tillo- 

 theridce, having molar teeth with distinct roots ; whilst the 

 other, Stylinodontidm, possessed rootless molars, which grew 

 from persistent pulps. All the known forms of the order are 

 from the Eocene Tertiary, and the typical species seem to 

 have been from one-half to two-thirds of the size of the 

 Tapir. 



