236 



NOTOUNGULATA 



ORDER VIII 



humerus has a low, simple trochlea, but no entepicondylar foramen. The 

 robust ulna with long, well-developed olecranon, and the short, somewhat 

 slighter radius, are crossed ; otherwise they are not unlike those of the 

 rhinoceros, and the same is also true of the pelvic girdle. The carpals are 

 alternating, the metacarpals short and thick (Fig, 319). The short femur has 

 a weak third trochanter ; its first trochanter is strongly projecting outward. 



Fic. 31ti. 



Toxodon paranensis Laurillard. Plio- 

 cene, Argentina. Fore foot, c, cuboid ; 

 I, lunar ; m, magnuui ; p, pisiform ; 

 sc, scaphoid ; td, trapezoid ; «, unciform. 



Fig. 320. 



Adinotheriuni sp. Upper Miocene (Santa Cruz 

 beds), Patagonia. A, Calcaneum, anterior aspect. 

 B, C, Astragalus, anterior aud posterior as- 

 pects. -Iz- 



The massive fibula may become fused with the tibia. The former articulates 

 inwardly with the stout calcaneum (Fig. 320 a). The astragalus (Fig. 320 b) 

 has a faintly arched and moderately deep trochlea, and its short, inwardly 

 directed neck has a weakly convex articular surface for the navicular. The 

 short, stout metatarsals and metacarpals have weak, obtuse keels. The end 

 phalanges form flattened hoofs. Manus and pes only have three digits each. 



Family 1. Notohippidae Ameghino. 



3.1.4.3. 



' ' • All of the teeth compactly set, hypsodont, with roots in old age, 



and intergrading gradually from the first incisor to the last molar ; in some cases 

 the lotoer incisors and canine may be chisel-shaped or spade-like, but never enlarged. 

 Cranial roof flat, nares terminal. Astragalus toith a rather long neck. 



The specialisation of the incisors and canines is not as strongly marked 

 in this family as in the Nesodontidae. The premolars and molars are still 

 covered with enamel on all surfaces. The posterior margin of the upper 

 molars forms a third ridge. The inflation of the mastoid region is very 

 slight in these forms. 



Notohippus Ameghino. Miocene of Patagonia. 



Bhynchippus Ameghino (Fig. 309 C, d). Incisors and canines chisel-shaped. 



Morphippus Ameghino (Fig. 309 c). Incisors and canines spade-like, the 

 incisor being like that of a horse. 



Coresodon Ameghino. Limited to the Lower Miocene ; Pyrotherium beds. 



