12 



UNGULATA. 



Hyracotherium cuniculus, Owen 1 . 



Syn. Macacus eoccenus, Owen 2 . 



This species appears to be distinguished from the last mainly by 

 its inferior size, the alleged difference mentioned by Owen in the 

 structure of the upper molars being apparently due to different 

 stages of wear. 



Hab. England. 



x & j 



36569. Two detached upper true molars of opposite sides, and two 

 specimens of the third right lower true molar ; from the 

 Lower Eocene of Kyson, Suffolk, The unworn upper 

 true molar shows very clearly the interrupted anterior 

 transverse ridge and the pronounced cingulum, considered 

 by Marsh as characteristic of the so-called Orohippus. 



Purchased, 1853. 



36572. Several detached upper and lower premolars ; from the 

 Lower Eocene of Kyson. Purchased, 1853. 



Hyracotherium angustidens, Cope 3 . 

 Syn. Orohippus angustidens, Cope 4 . 



This species is distinguished from the other American forms by 

 the great length of the premolars ; it is of small size. The lower 

 molars have a cingulum. 



Hab. North America. 



Fig. 3. 



Hyracotherium angustidens. — The last four left upper cheek-teeth ; from the 

 Wasatch Eocene of North America. \. 



M. 2561. Fragment of the left maxilla, containing the last four 

 {Fig.) cheek-teeth (see fig. 3); from the Wasatch Eocene of 



1 Ann. Mag. Nat. Hist. ser. 1, vol. viii. p. 1 (1841 ; the titlepage of the 

 volume is dated 1842). 



2 British Fossil Mammals and Birds, p. 5 (1846). 



3 Syst. Oat. Vert. Eocene N. Mexico: U.S. Geogr. Surv. W. of 100th 

 Meridian, 1875, p. 22 ; Orohippus. 



4 Loc. cit. 



