438 Eaton — John Day Felidce in Marsh Collection. 



terized, it is more truly feline than the canines of these 

 genera, being more nearly elliptical in section through- 

 out its length and less flattened on the inner surface. 

 The maximum (antero-posterior) diameter of the canine 

 at the alveolar margin is 15.5 mm. and the transverse 

 diameter 11 mm. Dividing the transverse diameter by 

 the maximum diameter, and multiplying the quotient by 

 100, an index of 71 is obtained. The corresponding 

 indices of the superior canines of several well-known 

 species of extinct Felidse are as follows : Nimravus 

 gomphodus 47, derived from Cope's measurements; N. 

 debilis 57 ; N. debilis major 56 ; Pogonodon platycopis 

 54 ; P. davisi 52, derived from alveolar diameters ; 

 Dinictis cy clops 64; D. felina 47. The diameters of the 

 superior canine of Pseudcdurus quadridentatus , at the 

 level of the neck, given by Filhol, 14 transverse 8 mm. and 

 antero-posterior 12.7 mm., yield an index of 71. In 

 examples of three recent feline species I find the corre- 

 sponding indices to be: Felis tigris 73; Felis concolor 81; 

 Cyncelurus jubatus 79. The vertical length of the canine 

 in the present species cannot be exactly determined 

 because of its imperfection. Its length, however, 

 appears to have been about the same, relative to the 

 length of the skull, as in Nimravus debilis; and relatively 

 less than in N. gomphodus. Except in young adult 

 animals the length of the canines is of course an unsatis- 

 factory quantity. The anterior ridge of the tooth lies 

 further back from the actual anterior margin than in 

 Nimravus, and in this respect also the present species is 

 further advanced and more cat-like. The posterior ridge 

 is not continued along the neck of the tooth to the alveo- 

 lar margin. This has much to do with the broad, ellipti- 

 cal section of the neck of the tooth. There is no trace, on 

 either side, of P 2 or its alveolus. For this reason two 

 premolars only are postulated in the dental formula 

 stated above. If in early adult life there was a P 2 , it can 

 hardly have been other than exceedingly small and 

 vestigial, as the shortness of the postcanine diastema, 

 9.5 mm. on one side and 10 mm. on the other, renders the 

 presence of a P 2 of any considerable size highly improb- 

 able. The shortening of the postcanine diastema with 

 reduction of P 2 to vestigial size would have practically 

 the same significance as the shortening of the diastema 



14 H. Filhol, Annales des Sciences Geologiques, 21, 76, 1891. 





