158 



University of California Publications in Geology [Vol. 10 



In addition to the skull material contained in the collections of the 

 Museum of History, Science and Art of Los Angeles, there are also 

 available for comparison five mandibles as well as fragments of 

 mandibles of Nothrotherium from the asphalt beds. These specimens 

 show a considerable range in size. No. 636 represents one of the 

 smaller individuals and approximates very closely in size the frag- 

 mentary ramus, no. 8-122 Univ. Calif. Coll. Palae., from Potter Creek 

 Cave. The latter if anything is slightly smaller than no. 636. The 

 differences between the specimens are slight. The tooth-row in no. 

 8122 is a trifle longer; the postero-external opening of the dental 

 canal is small and the ascending portion of the ramus behind Mj is 

 apparently a little thicker than in no. 636. On the whole the char- 

 acters presented by the fragmentary ramus from Potter Creek Cave 

 are hardly to be distinguished from those of the Rancho La Brea 

 specimens. 



Associated with the ramus of N. sliastense from Potter Creek Cave 

 are a number of teeth, one of which Sinclair 34 identified as a last 

 superior tooth. He describes this specimen as follows: "It is a tri- 

 angular tooth with the posterior side plane, the anterior convex, and 

 the outer plane and meeting the posterior at a right angle." 35 A com- 

 parison of this tooth with the last superior alveolus of skull 15 from 

 Rancho La Brea showed that the latter must have possessed a M 5 

 which differed markedly from Sinclair's specimen. This has been 

 amply verified by the additional material now available. The shape 

 of the tooth in the species from the asphalt beds is remarkably con- 

 stant. It differs from the corresponding tooth, no. 8497 Univ. Calif. 

 Coll. Palae.. from Potter Creek Cave in (1) subtrapezoidal outline. 

 (2) outer and inner sides of equal thickness. (3) posterior face con- 

 cave transversely, (4) presence of vertical groove on outer face and 

 faint vertical groove on inner face near anterior border, and (5) outer 

 and anterior faces concave longitudinally. 



The differences noted are undoubtedly great enough to separate 

 the Rancho La Brea form as a distinct species, if Sinclair's specimen 

 can be regarded with certainty as a last superior tooth of Notliro- 

 therium. A critical re-examination of this tooth has convinced the 

 writer that there are, however, serious objections to its being considered 

 as such. As stated by Sinclair, no. 8497 (fig. 9) has been somewhat 



34 Sinclair, W. J., New mammalia from the quaternary eaves of California, 

 Univ. Calif. Publ. Bull. Dept. Geol., vol. 4, pi. 23, fig. 8, 1905. 



35 Sinclair, W. J., ibid., p. 154. 



