1374 



CLASS MAMMALIA. 



referable to the present family, which is evidently a very ancient 

 branch of the suborder, and may, it is suggested, have been 

 directly derived from the Condylarthra. 



Family Titanotheriid^e. — This extinct family, equivalent to the 

 Brontotheriidce of Professor Marsh and the Menodontidce 1 of several 

 other writers, is so closely connected by Diplacodon with the Lambdo- 

 theriidce, that Dr Schlosser has proposed to unite the two. In the 

 present family at least the fourth upper premolar has two inner 

 columns, and is thus as complex as the true molars ; while in those 

 forms of which the limbs are known there are four anterior and three 

 posterior digits. The third trochanter of the femur is rudimentary. 

 Paired bony protuberances may be present in the fronto-nasal region 

 of the skull. In Diplacodon, of the Eocene of North America, only 

 the fourth upper premolar is as complex as the true molar; the 



canines are as large as in Paiceosyops ; the incisors -' are small ; 



(3) 

 and the skull has no bony protuberances. 



The type genus Titanotherium, which Messrs Scott and Osborn 

 consider should include Menodus (preoccupied), Megacerops, Bron- 

 totherium, Diconodon, and probably Symborodon, is confined to the 



Fig. 1249. — Left lateral aspect of the cranium of Tit another itan coloradense ; from the 

 Miocene of North America. Greatly reduced. (After Marsh.) 



Miocene of North America, and comprises animals of huge bulk ; 

 and it is probable that the forms recently described by Professor 

 Marsh under the names of Allops, Brontops (fig. 1250), and Menops 

 are not really separable. An entire skeleton is shown in fig. 1250, 

 and a cranium in fig. 1249. The number of teeth is subject to a 

 variation analogous to that obtaining in Rhinoceros, this variation 



( 2 -3) n 1 z>„„ -4 „, 3 



being expressed by the formula I. 



(o-3X 



C. -, Pm: 



(3-4)' 



M. 



1 The name Menodus is the earliest of those applied to these animals, but is in- 

 admissible on account of the earlier application of Menodon to a fossil reptile. 



