THE SANTA CRUZ TYPOTHERIA. 



(Figures i-io.) 



By WILLIAM J. SINCLAIR. 



(Read April 24, 190S.) 



The Typotheria are a group of semi-ungulate mammals of strictly 

 South American origin appearing first in the Notostylops beds of 

 Patagonia.^ During the Santa Cruz epoch four genera are repre- 

 sented but what is lacking in generic and specific diversity is more 

 than compensated for by an abundance of individuals. The total 

 number of common species apparently does not exceed eight, but this 



Fig. I. Skull of Protypothcrium australc Ameghino, side view, three 

 fourths the natural size. (No. 9565 American Museum of Natural History 

 collection.) 



has been increased to no less than fifty-one by failing to estimate 

 at their true value characters due to age and others which seem to 

 be of the nature of individual variations in size, the result no doubt 

 of the extremely fragmentary character of the material hitherto 

 available. Even with the large suites of specimens in the collections 



' Isotypothcrium, Epitypothcrinm. 



64 



