THE ASTRAPOTHERES AND THEIR KIN 



1149 



jaws. Macrauchenia itself, which was discovered by Darwin in the superficial deposits 

 of Patagonia, was an animal somewhat larger than a horse, presenting the remarkable 

 peculiarity of having the aperture of the nostrils in the skull situated in the middle 

 of the forehead; although during life it is probable that they terminated in a short 

 trunk. In the lower, or Miocene Tertiaries of Patagonia the family was represented 

 by smaller and less specialized forms (such as Oxyodontotherium] , in which the nos- 

 trils were more normal in position, and the crowns of the molar teeth lower and simpler. 

 In the second family, or Proterotheriidce ', represented principally in the lower 

 Patagonian Tertiary deposits, the teeth were reduced in number, and formed an unin- 

 terrupted series, a pair in both the upper and lower jaws being much longer than the 

 rest. In these proterotheres the molar teeth had a considerable resemblance to those 

 of the palseotheres; but the feet were of the general type of those of the three-toed 

 horses, or hipparions, and in some cases it appears that only the middle toe was 

 functionally developed. 



THE ASTRAPOTHERES AND THEIR KIN 

 SUBORDER Astrapotheria 



In this second South-American group, represented only in the Miocene deposits 

 of Patagonia, all the species 

 are of large size, and possess 

 rooted cheek-teeth of a rhi- 

 nocerotic type, and lacking 

 the marked curvature of the 

 crown characterizing those of 

 the toxodonts. The verte- 

 brae of the neck are com- 

 paratively short, with flat- 

 tened articular surfaces, and 

 the lateral canal piercing the 

 transverse process in the 

 ordinary manner. The wrist 

 and ankle joints were prob- 

 ably of the linear type; the 

 calcaneum articulated largely 

 with the fibula; and the 

 astragalus was quite flat, and 

 furnished with a large head 

 for articulation with the 

 navicular bone. The femur, 

 when known, had a large 

 third trochanter. 



In both families the up- 

 per cheek-teeth were of a 

 rhinocerotic type of structure, having a continuous external wall undivided into 



PALATE OF THE HOMALODONTOTHERE, WANTING 



SOME OF THE FRONT TEETH. 



(Much reduced.) 



