30 Litopterna, Perissodactyla (Uneven-toed Ungulates). 



Sub-order 8. — Litopterna. 



Pier-case 

 No. 20. 



This is also a South American group and includes a number 

 of animals which in their foot and tooth structure resemble the 

 nneven-toed Ungulates (Perissodactyla), though they are not 

 related to them. In the collection are jaws and teeth of Protero- 

 therium and Piadiaphorus belonging to the Proterotheriidce. 

 Some of the members of this family possess feet which much 

 resemble those of Hipparion, the third toe being very large and 

 the second and fourth short and very much reduced. These 

 specimens were presented by Dr. F. P. Moreno. 



The second family, the Macrauchenildce, is represented by 

 remains of Macrauchenia patagonica, including a ramus of a 

 mandible and portions of limb- bones from the Pleistocene 

 deposits of Buenos Ayres, in South America ; also plaster casts 

 of a vertebra, a femur, bones of a fore-foot, and other remains, 

 discovered by Charles Darwin at Port St. Julian, South Pata- 

 gonia, and described by Sir Richard Owen.* 



Some additional specimens have lately been received from 

 Dr. Moreno. In the older Tertiary deposits of Patagonia is 

 found a smaller form named Oscyodontotherium, which is 

 closely allied to Macrauchenia and may be ancestral to it ; this 

 is represented in the collection by teeth and limb-bones exhibited 

 in this case. 



Sub-order 9. — Perissodactyla (uneven-toed Ungulates). 



Uneven-toed 

 TTng-ulata. 



TJng-ulata. 

 Perissodac- 

 tyla. 



This group of hoofed herbivorous mammals is represented 

 at the present day by the Rhinoceros, f Tapir, and Horse. 

 Although not numerous in species, they are very widely dis- 

 tributed over the earth's surface, and their ancestors, even as 

 far back as the Eocene Tertiary period, formed a "very extensive 

 and varied assemblage of animals. 



The middle or third digit on both the fore and hind feet, 

 which is always present, is the largest, and is symmetrical in 

 itself, and occupies the middle line of the foot. 



In the Tapir four functional toes are present on the fore- 

 foot ; in the Rhinoceros three ; and in the Horse only the third, 

 or middle toe, remains. (See Fig. 38, A, b, C, p. 31.) 



* See Fossil Mammalia, Yoyage of the '-'Beagle," 1839. 



f A skeleton of the modern Indian Rhinoceros is placed in the centre of 

 the Gallery, near the Pier-cases containing the fossil species, for comparison 

 with them. 



