66 



Equus principalis, Lund '. 



Syn. Equus macrognathus, Weddell 2 , 



Equus neoffcem, P. Gervais 3 (non Lund). 

 Hippidion principalis, Owen 4 . 

 Equus arcidens, Owen 5 . 

 Hippidion arcidens, Owen 6 . 



The writer follows Burmeister (' Die fossilen Pferde der Pampas- 

 formation,' p. 61 [1875]) in identifying E. arcidens with the present 

 form. The species is of larger size than E. neogceus, Lund, and has 

 the crowns of the upper cheek-teeth very short, much curved, and 

 with a small anterior " pillar," which is not larger than the posterior. 

 The first upper premolar is present. 



Hob. S. America. 



40492. Five upper cheek-teeth ; from the Pleistocene of Arroyo, 

 (Fig.) Gutierrez, near Paysandu, Uruguay. These specimens 

 are the types of E. arcidens, and are described and figured 

 by Owen in the Phil. Trans, for 1869, p. 566, pi. Ixii. 

 figs. 1-8 ; they agree precisely with the corresponding 

 teeth in the complete dental series figured by Burmeister, 

 op. cit. pi. iii. fig. 3. 



Presented by W. G. Lettsom, Esq., 1867. 



18095. A left upper cheek-tooth ; from a cavern in Minas Geraes, 

 Brazil. Olaussen Collection. Purchased, 1845. 



Equus sivalensis, Falconer and Cautley ~. 



This species, with which Forsyth-Major * identifies Equus stenonis, 

 Cocchi 9 , occurs in the Pliocene Siwaliks of India. The first upper 

 cheek-tooth is frequently retained, and mm. 1 is present in one 

 instance, the anterior pillars of the upper true molars are very short 

 antero-posteriorly (thereby indicating affinity with Hippariori) ; the 

 diastema is shorter than in E. caballus, and there is a trace of a 

 " larmial " depression on the maxilla. The cranium comes nearer 



K. Danske. Vid. Selsk. Skr. Tol. xii. p. 89 (1846). 



Voyage dans le Sud de la Bolivie, p. 204 (1851, forming vol, vi. of Castelnau's 

 Expedition, ' Hist. d. Voyage'). 



Rech. s. Main. FOBS, de 1'Amerique Me>idionale, p. 33 (1855). 



Phil. Trans, for 1869, p. 573 (1870). 5 Loc. cit. p. 559. 



Loc. cit. p. 572. 



' Fauna Antiqua Sivalensis,' pt. 9, pi. Ixxxi. (1849). 



Quart. Journ. Geol. Soc. vol. xli. p. 2 (1885). 



Mem. Soc. Ital. Sci. Nat. vol. ii. art. 7, p. 14 (1867). 



