20 



University of California Publications. [Geology 



jaw of M. josephi, and may represent that species. This speci- 

 men (No. 364) shows distinctly the structure of P 2 , which has not 

 been described in Mesocyon. This tooth has both anterior and 

 posterior basal tubercles in addition to a well-developed posterior 

 cusp. The heel of the sectorial, although slightly damaged, seems 

 to differ from that of the typical Mesocyon coryphaeus. The 

 hypoconid is somewhat smaller and lower, and the entoconid is 

 relatively larger, the type of heel being as well adapted to crush- 

 ing as to cutting. M 2 and M s are represented only by the roots 

 and alveoli. They both appear to have been relatively large teeth, 

 and M 3 had two roots instead of one as in coryphaeus. If this is 

 M. josephi there may be reason to believe that this species is a 

 characteristic form of the Middle John Day, while the larger 

 coryphaeus seems to have been common in the Upper John Day, 

 though possibly present in the middle division also. 



MEASUREMENTS. mm. 



M I( anteroposterior diameter 15.5 



P 4 , antero-posterior diameter 8.8 



P,, antero-posterior diameter 7 



Height of jaw below protoconid of M t 16 



Height of jaw below protoconid of P 2 15 



INDETERMINATE. 

 Text-figures 4, 5, and 6. 



Several loose teeth, which have not been connected with de- 

 terminable specimens, show peculiar characters of the inferior 

 molars not recognized as yet in any of the John Day canids. In 

 text-figure 4 there is shown the heel of a M, and a perfect M 3 

 preserved in a jaw fragment (No. 672) found at the same lo- 

 cality in the Middle John Day beds with specimen No. 364 

 tentatively referred above to M. josephi. In this specimen the 

 entoconid and hypoconid of M 2 are both well developed. M 3 is 

 a broad tooth with a large talon. The small protoconid and the 

 metaeonid are very close together, and the paraconid shelf is 

 much reduced. The entoconid and hypoconid are larger and 

 farther apart than the tubercles of the trigon. In Mesocyon 

 coryphaeus the talon of M 2 supports a single tubercle. The sec- 

 ond and third inferior molars of M. josephi are unknown, though 



