144 THE DESEADO FORMATION OF PATAGONIA 



in the lower series. The Deseado forms are also of con- 

 siderably larger size than the Santa Cruz. 



Our material includes a pair of lower jaws, two scap- 

 ulae, the humerus, and the lower end of the femur. 



No skull has been found in the Deseado. Those from 

 the Santa Cruz are enormously swollen over the orbits, 

 the massive bone making a skull wholly unique. The 

 lower jaws are similar to those of Astrapotherium, except 

 that the rami are deeper. The front ends are fused and 

 expanded making the anterior much enlarged, and causing 

 the incisors to stand at intervals as in Coryphodon. The 

 symphysis is massive and prolonged backward nearly to 

 premolar 3. The rami are plump and unusually thick. 



Fig. 102. Upper dentition of Astrapothericulus iheringi 

 1/2 natural size. 



Of the upper dentition, Ameghino figures only the first 

 molar and the canine. I have given Ameghino's figure 

 of the upper dentition of Astrapothericulus, to indicate 

 what this would be like, for the variation is only slight. 

 The canine is a great tush, not unlike the incisor-tush of 

 Pyrotherium, oval in cross section with the greater diameter 

 from front to back. The first and second premolars have 

 disappeared. Premolars 3 and 4 are greatly reduced. 

 The molars are very like those of Asmodeus, large brachy- 

 dont grinders, composed of an outer wall, and an anterior 

 and posterior lobe. The external cingulum is a trace 

 only, and the internal cingulum is developed in varying 

 degrees. The basin is deep and subdivided by a crista 

 which rises from the external wall, and as the surface is 

 worn off unites with the anterior lobe, cutting off a small 



