Eaton — John Day Felidce in Marsh Collection. 445 



For the other species of Dinictis this index has not been 

 computed, but, judging from published illustrations none 

 of them appear materially to exceed D. cyclops in the rela- 

 tive posterior palatal breadth. The entire posterior por- 

 tions of the maxillae, including the zygomatic processes, 

 are exceedingly massive, and the palatine processes of the 

 maxillae, instead of forming thin, sharp-edged orbital 

 floors, as in the examples of Nimravus, Pogonodon, and 

 Dinictis that I have examined, are thick and rounded 

 posteriorly. The palatal vault is much deeper than in 

 Nimravus. This is caused, not by a more pronounced 

 arching of the palatines and the palatine processes of 

 the maxillae, but entirely by the greater vertical depth 

 of the alveolar processes which form the sides of the 

 vault. A direct result of this modification is seen in the 

 almost complete elimination of the circular pits, in the 

 palatine processes of the maxillae, that in Dinictis, Nimra- 

 vus, Pogonodon, Pseudcelurus, and Hoplophoneus receive 

 the principal cusps (protoconids) of the lower carnas- 

 sials when the jaws are closed. Slight irregularities in 

 the contours of the maxillae, at the lowest points of origin 

 of the masseter muscles, are by no means uncommon in 

 the Felidae, recent and extinct, and osteological peculiari- 

 ties of this description would probably be most noticeable 

 in middle-aged individuals of large size and robust form. 

 Accordingly caution must be exercised lest too much 

 importance be given to differences that may be due solely 

 or largely to individual variation. It would, however, 

 be a serious omission to fail to note the form of the 

 maxillae immediately external to the superior molars in 

 the present species. On each side of the skull, the power- 

 ful development of the masseter muscles has apparently 

 caused changes in the maxillary contours amounting 

 almost to the production of bony masseteric processes. 

 The lack of symmetry, displayed on the two sides, 

 must of course be attributed to individual variation, yet 

 so pronounced is the smaller outgrowth on the left side, 

 that, in view of the unusually massive character of the 

 entire fore part of the skull, it may properly be regarded 

 as of at least specific value. In this connection, the 

 following quotation from "Wortman's 15 description of 

 Dromocyon vorax is of interest: "On the under surface 



15 J. L. Wortman, This Journal (4), 12, 293, 1901. 



