144 PROCEEDINGS OF THE PALEOXTOLOGICAL SOCIETY 



Paramijlodon Bro\Yn was untenable. The skulls appeared to be all referable 

 to a single species of the genus Mylodon. 



Discussion 



Doctor Matthew noted the fact that the type of Paramylodon and of the 

 recently described species Mylodon garmani Allen were both from the same 

 quarry, and pointed out that the Santa Cruz ground sloths also showed a 

 remarkably wide range of variation in characters comparatively constant in 

 other gi'oups of mammals. On the other hand, the ground sloths of the 

 Pampean formation appeared to have their characters more fixed. Rapid evo- 

 lutionary progress or the invasion of a new environment were iwssible causes 

 of this wide range of individual variability. 



GEOLOGY OF THE UINTA FORMATION 

 BY EARL DOUGLASS 



Presented in abstract by Professor Osborn. 



NEW TITANOTHERES FROM THE UINTA FORMATION OF UTAH 

 BY A. O. PETERSON 



Presented in abstract by Professor Osborn. 



Two new genera of Eocene Titanotheridre were described, one of which has 

 already well developed horns. 



Discussion 



Doctor Gregory inquired as to the iwssible identity of one of the new genera 

 with Diplacodon Marsh. Pi'ofessor Osborn replied that he presumed that it 

 had been compared and found distinct. 



REPORT OF PROGRESS IN THE REVISION OF THE LOWER EOCENE FAUNAS 

 J BY W. D. MATTHEW 



The author stated that the revision was based on the large collections 

 secured by American Museum parties in charge of Mr. Granger in 1905 and 

 1909-1913. Detailed studies of the stratigraphy had been made by Doctor 

 Sinclair and Mr. Granger, and careful record kept of the exact locality and 

 level of every specimen. This made possible a more exact correlation of the 

 different terranes and a division of the Lower Eocene into four distinct faunal 

 zones. A fifth zone was referred to the top of the Paleocene. The systematic 

 revision of the fauna was being conducted by Mr, Granger, Doctor Sinclair, 

 and himself, especially with the aid of topotypes. Doctor Gregory had under- 

 taken studies on the morphology and affinities of certain groups. The collec- 

 tions included many new genera and species and more complete specimens of 

 most of these already known. Among the most interesting of the new types 

 were two which appeared to be of South American affinities, related re- 

 spectively to the armadillos and the homalodotheres. The progressive evolu- 



