EHINOCEROTID^;. 



141 



M. 2742. Cast of the fourth right lower premolar. The original is 

 from the Lower Miocene of Weinsheim, Hessen-Darm- 

 stadt ; and is figured by Kaup in the Oss. Foss. d. Darm- 

 stadt, pt. 3, pi. xii. fig. 11. 



Eyerton Collection. Purchased, 1882. 



E. Aceratherine Group. 



In this group there is no nasal horn, and the nasals are straight 

 and flat. In the typical R. incisivus and some other European species 

 there are four digits to the manus, but in others, as well as in the 

 North- American forms (which have been generically separated), they 

 are reduced to three. The number of cutting-teeth ' is various, and 

 may, according to Cope, be represented by the formula I. ^ L - ) , C. -^ 



Fig. 16. 



Ehinoceros megalodus (Cope 2 ). Skull ; from the Miocene (Loup Fork Beds) of 

 Colorado. . (From the ' American Naturalist.') 



1 For the dentition of the American forms see Cope, Proc. Amer. Phil. Soc. 

 yol. xix. p. 393 (1881). In this memoir the formula of the so-called Peraceras 



is given as I. r-, C. j- ; it was given in the Amer. Nat. vol. xiv. p. 540 (1880) as 



I. Q, C. Q , and is thus quoted in the ' Palaeontologia Indica,' ser. 10, vol. ii. 



p. ix. (In note 1 the volume and sheet [xiv. 1880] are omitted.) 



2 Syn. Aphelops megalodus, Cope. 



