232 NOTOUNGULATA order viii 



beginning far hehind the maxilla. Mandible high. Jugal with a downwardly 

 directed process. Tibia and fibula free. Outer toes reduced. 



Proti/potherium (Patriarchus) Ameghino (Figs. 309b, 310, 312, 314). Jugal 

 with small process. Teeth gradually transitional from one form to the other. 

 Miocene of Santa Cruz. F. australe, P. attenuatum Ameghino. 



Interatherium (Icochilus) Ameghino (Fig. 315). Lateral incisors and 

 canines reduced. Jugal with well - developed process. Humerus with 

 indistinct foramen. Miocene of Santa Cruz. /. robustum, I. extensum Ameghino. 



Cochilius Ameghino. Miocene. Colpodon beds. 



Plagiarthrus Ameghino. Teeth rooted in old age. Pyrotherium beds. 



Family 3. Hegetotheriidae Ameghino. 



I-^ is enlarged. P^ and P^ are molariform. Upper molars are convex on the 

 inner side, outside they are smooth. Mastoid is hollow, malar adjacent to maxilla. 

 Tibia and fibula fused. Outer toes unequally reduced. 



Hegetotherium (Selatherium) Ameghino. ' ' ' ' • Posterior incisor and 



canine somewhat reduced. Terminal phalanges flattened. Tail long. About 

 the' size of a fox. Miocene. Colpodon and Santa Cruz beds. H. mirabile 

 Ameghino. 



Archaeopilus, Prohegetotherium Ameghino. Lower Miocene. Pyrotherium 

 beds. 



Prosotherium Ameghino. ' ' ' • Pyrotherium beds. 



Eohegetotlierium Ameghino. Teeth with roots. Oligocene. Astraponotus 



beds, 



1.0.3.3. 

 Pac^yrwcos Ameghino (Paeio^^miAmBurmeister). ' ' ' • Mastoid region 



extremely inflated. Terminal phalanges hoof-like. Tail short. Miocene. 



Santa Cruz. P. moyani Ameghino. About the size of a rabbit. Occurs in the 



Colpodon beds and also in the Pliocene and Pleistocene. Monte Hermoso. 



P. typicus Ameghino. 



Eopachyrucos, Pseudopachyrucos Ameghino. Astraponotus beds. Propachy- 



rucos Amegh. Pyrotherium beds. 



3.1 4.3. 

 Argyrohyrax Ameghino. ' ' ' ' • The last incisor, the canine and P^ 



and P' gradually leading from one form to the next. P^ and P^ are molari- 

 form. Pyrotherium beds. 



Family 4. Typotheriidae Ameghino. 



1.0.2.3. 

 ' "' ' • /^ broad, bent and open at the base, with enamel on the front surface. 



/<, small. Behind the incisors there is a long diastema. Upper premolars with 

 two, molars with three ridges. Anterior moiety of the lower molars much shorter 

 than the posterior. All the molars are prismatic and partially covered with cement. 

 CarpaJs alternating. Manus with slender pollex. Fibula not articulating with the 

 calcaneum. 



