98 University of California Publications in Geology ITol. 10 



element (figs. 15a to 15c) is slightly longer and considerably more 

 massive than that of specimens of Aretotheriuni simum from Potter 

 Creek Cave and from Bancho La Brea. This difference between the 

 Oregon form and the California Bleistocene Aretotheriuni is well 

 shown in transverse diameter and thickness of the narrowest portion 

 of the shaft at the lower end of the pectoral ridge. The supinator 

 ridge is strongly developed as in A. simum, and is higher or wider 

 than in either the Potter Creek Cave or the Bancho La Brea specimens. 

 The flat area between the deltoid and pectoral ridges is more strongly 

 marked and wider than in the California Pleistocene Aretotheriuni 

 specimens. The lower end of this area also extends relatively 

 much nearer the distal end of the shaft than in A. simum, and in side 

 view (fig. 15c) is seen to project farther anteriorly. A large ent- 

 epicondylar foramen is present as in Arctotherium. The bar of bone 

 forming the outer boundary of this foramen is largely broken away, 

 but the remaining portion appears relatively heavier than in Arcto- 

 tlu num. The upper end of the foramen seems more broadly rounded 

 than the superiorly narrowed foramen in A. simum. 



( hi the whole the humerus is of a much more massive type than 

 that of the California Arctotherium, and in this respect suggests the 

 relatively heavy skeletal elements of Hyaenaretos. 



The proximal half of the right ulna (figs. 16a and lQb) resembles 

 in many respects the corresponding element of Arctotherium simum, 

 but it is much larger and more massive than the California Pleistocene 

 specimens. The anteroposterior diameter or greater width of the 

 shaft seems relatively longer in no. 12!23<>12 than in the Arctotherium of 

 California, and one might assume that in the Pliocene form this 

 element was relatively somewhat stronger and heavier. The olecranon 

 region of no. 22.'!(>2 is longer than in A. simum and the anterior 

 tuberosity of the olecranon is considerably higher. The posterior 

 region of the olecranon is sharply twisted toward the inner side as in 

 Ursus and Arctotherium. The anterior tuberosity is separated from 

 the twisted posterior angle of the olecranon by a sharply marked 

 concave surface which is not represented on the olecranon in Arcto- 

 lli< rium and Ursus. The greater sigmoid cavity is deep and the lesser 

 sigmoid cavity is distinctly concave. 



in no. 22362 the ulna differs from a specimen described as Hyaen- 

 aretos from the Siwaliks of the Saharanpur district by Lydekker. 3 

 The Indian specimen was assumed by Lydekker to represent Hyaen- 



3 Lydekker, R., Records, Geol. Survey of India, vol. 21, part 4, p. 143, 1888. 



