44:0 Eaton — John Day Felidce in Marsh Collection: 



by the inner root be disregarded, than in Nimravus. M 1 

 is a very small tooth, and the reduction of its inner lobe 

 has proceeded so far that the transverse diameter of the 

 tooth-crown is not greater than the antero-posterior 

 diameter. Since the external margins 'of the premaxillse, 

 between the canines and the lateral incisors, are widely 

 and deeply concave, when viewed from above or below, 

 it may be inferred that the lower canines, which were 

 given clearance by these concave diastemata when the 

 jaws are closed, were also of larger transverse diameter 

 than those of Nimravus; and this inference is supported 

 by fragments of a lower canine that were found embedded 

 in the matrix. So deeply concave are these precanine 

 diastemata that they extend further to the rear than 

 the anterior margins of the maxillary parapets enclosing 

 the canine alveoli. 



Cranium. — The skull in its general proportions shows 

 a greater resemblance to Nimravus and Dinictis than to 

 Hoplophoneus. From Pogonodon, which is in some 

 respects intermediate between Dinictis and ■ Hoplo- 

 phoneus, it is not so distinctly separated by cranial pro- 

 portions as by dentition. The foramina of the 

 basi-cranial region, the height of the glenoid articulations 

 relative to the base-line of the skull, and the form and 

 position of the mastoid processes are essentially the same 

 in the present species as in Nimravus; but in the wide 

 spread of its zygomatic arches and in the breadth and 

 massiveness of the entire fore part of the skull — charac- 

 ters that have suggested the specific name — the present 

 species departs widely from the proportions of the 

 species of Nimravus and Dinictis. 



With a basal length of 174 mm., measured from basion 

 to prosthion, the bizygomatic diameter is 164 mm. The 

 relation of these measurements is expressed by the bizy- 

 gomatic index of 94, which is well outside the range of the 

 corresponding indices of Nimravus, Dinictis, and Pogono- 

 don. The bizygomatic indices of the best known species 

 of the three above-named genera are as follows : Nimravus 

 gomphodus 72; N. debilis 76; N. debilis major 71; 

 Pogonodon davisi 74 (approx.) ; P. platycopis 78 

 (approx.) ; P. serrulidens 11 (approx.) ; Dinictis cy clops 

 85 ; D. squalidens, No. 8777, A. M. N. H, 82 ; D. felina 

 76; D. paucidens 79; D. fortis 82 (from illustration). 



