BIG BADLANDS OF SOUTH DAKOTA. 493 



Function of the Dependent Malar Processes. 



Incidentally this has a bearing on the function of the jugal 

 process. Mr. Troxell thinks that it " in all probability gave origin to 

 the masseter muscle which generally arises from the jugal and is 

 inserted broadly on the wide angle of the ramus," and that " from 

 the tip of the process the fibers of the muscle might have given the 

 forward, the backward and even a sideward movement of the man- 

 dible. . . ."^^ It seems to me equally probable that the process in 

 question extended over the masseter without giving origin to it, and 

 projected sufficiently beyond the outer surface of the cheek to afford 

 a handy grip to an antagonist. In A. scotti, No. 10885, both out- 

 ward curvature and relative length of the cheek process are some- 

 what increased by the distortion of the specimen. 



Resume. 



Restricting the survey to the Big Badlands of South Dakota and 

 combining data from the Yale and Princeton collections, we have the 

 following range of forms in time : 



I. Titanotherium beds. 



Archceotherium scotti sp. nov. 

 Arclicpothcrinin inarshi Troxell.^^ 



II. Oreodon beds. 



Archceotherium wanlessi sp. nov. 

 Archceotherium mortoni Leidy. 

 Archceotherium ingcns Leidy. 

 Archceotherium crassum? (Marsh). 



III. Protoceras beds. 



Megachcerus zygomaticus Troxell. 

 Megachcerus latidens Troxell.^* 



12 Loc. cit., p. 25s. 



13 North bank of Cheyenne River between French Creek and Battle 

 Creek, South Dakota, associated with Brontotherium and Hyracodon. Trox- 

 ell, loc. cit., p. 386, footnote. 



14 Probably Upper Oligocene, near Cheyenne River, South Dakota. Trox- 

 ell, loc. cit., p. 437. 



