igoS.] 



SINCLAIR— THE SANTA CRUZ TYPOTHERIA. 



67 



Fig. 2. Skull of Intcrathcrium robiistiiin Ameghino. side view, three 

 fourths the natural size. (No. 9263 American Museum of Natural History 

 collection.) 



I. The Skull. — The facial portion of the skull is slender and 

 more or less excavated longitudinally while the brain case is broad 

 and well expanded. The orbits are central, circular in outline, quite 

 prominent in Hegetothcriimi, Pachynikhos and Intcrathcrium and 

 unenclosed posteriorly. The jugal arches are robust in all except 



Fig. 3. Skull of Hcgctotlicrium mirahilc Ameghino, side view, three fourths 

 the natural size. (No. 15542 Princeton University collection.) 



Pachyrukhos and moderately expanded. The premaxillse are short 

 and heavy with scarcely any ascending process ; the nasals are broad 

 posteriorly, tapering forward to blunt points ; the interorbital tract 

 plane and the sagittal and lambdoidal crests low. The most promi- 



