166 UNGULATA. 



Family MACRAUCHENIID^. 



Of this family only the type genus is at present known, and the 

 characters of the latter may therefore be taken as those of the former 1 . 



Dentition: 1. J, C. \, Pm. J, M. f. 



The cheek-teeth are rhinocerotine, the upper true molars pre- 

 senting two external V's and two transverse crests ; there is only a 

 very short diastema in the upper jaw. The cervical vertebrae re- 

 semble those of the Camelidce in the position of the vertebr arterial 

 canal, but the extremities of their centra are flat. The fibula articu- 

 lates with the calcaneum (a character not known in any other 

 Perissodactyle) ; and there are three digits to each foot, the lateral 

 digits being of large size. Schlosser 2 regards the structure of the 

 limbs as extremely primitive, and the dentition as more specialized. 



Genus MACRAUCHENIA, Owen 3 . 

 Macrauchenia patachonica, Owen 4 . 



This is the type species. 

 Hob. South America. 



19950. The greater part of the left ramus of the mandible, showing 



(Fig.) all the cheek-teeth except p m . 1 ; from the Pleistocene of 



Buenos Ayres. Described and figured by Owen in his 



' Odontography,' p. 35, pi. cxxxv. fig. 7, and in the Phil. 



Trans, for 1870, p. 79, pi. viii. figs. 1-3. 



Purchased, 1846. 



43247. The distal half of the right humerus ; from the Pleistocene 

 of Buenos Ayres. 



Presented by Senor L. J. Fontana, 1871. 



M. 2706. Cast of the right metacarpals and many of the phalan- 

 geals. The original of these and the other casts are the 

 type specimens, and are preserved in the Museum of the 

 Royal College of Surgeons ; they were 'obtained from the 

 Pleistocene of Port St. Julian, Patagonia, and are de- 

 scribed and figured in the ' Voyage of the Beagle.' 



Presented by the Royal College of Surgeons, 



1 See Burmeieter, ' Deacripcion de la Macrauchenia patachonica ' (Buenos 

 Ayres, 1864). 



2 Zool. Aiizeig. no. 210, 1885. 



* Zoology of H.M.S. 'Beagle,' pt. i. p. 35 (1840). 

 4 Loc. cit. 



