Eaton — John Day Felidce in Marsh Collection. 447 



canal passes through the basioccipital, but I am inclined 

 to believe that such is not the regular occurrence in 

 Dinictis, for in Matthew's detailed figure of the basi- 

 cranial region of Dinictis, 20 presumably drawn from the 

 excellent specimen of Dinictis squalidens , No. 8777, 

 A. M. N. H., the entrance to the carotid canal is appar- 

 ently through an open notch in the lateral expansion of 

 the basioccijntal, and precisely the same condition has 

 been observed in a skull in the Marsh Collection, Yale 

 University, Cat. No. 10048, identified as Dinictis squali- 

 dens. The otic bullae, although incomplete, are much 

 more fully developed than in Nimravus, a considerable 

 portion of the thin wall of the bulla, on each side, being 

 preserved in extension of the thickened tympanic ring, 

 and traces of the median walls of the bullae being visible, 

 closely pressed against the lateral expansions of the 

 basi-occipital. In this respect the present species shows 

 a decided advance beyond the stage reached by Nimra- 

 vus; and a like further development toward the recent 

 Felidae may be observed in the shortened length of the 

 alisphenoid canal and in the slenderer proportions of the 

 bridge of the alisphenoid bone, protecting the external 

 carotid artery at this point. The brain-chamber appears 

 to have been a little larger, in proportion to the basal 

 length of the skull, than in Nimravus, but this superiority 

 may be more apparent than real, since external measure- 

 ments only are available, and it is possible that the cran- 

 ial walls of the present species, in keeping with the 

 robust development of the skull generally, may be slightly 

 thicker than in the species with which comparison has 

 been made. 



The fossil skull and the hard ashy matrix are very 

 light gray in color, and so appear to satisfy the require- 

 ments of the upper John Day beds, as they occur in the 

 Cove on the John Day River, where the record states 

 the specimen to have been found. This reference of the 

 type to the upper John Day is further supported by the 

 advance, shown in certain cranial and dental characters, 

 beyond the stage of evolution denoted by Nimravus 

 debilis and Nimravus debilis major, both of which species 

 are understood to be from the middle John Day. 



20 W. D. Matthew, Bull. Am. Mus. Nat. Hist., vol. 28, 299, 1910. 



