G. I. Adams — Extinct Felidce of North America. 443 



There is a point of difference among the two sub-families 

 which should be discussed here. It is the character of the 

 basi-cranial foramina which was made by Cope a basis of classi- 

 fication. The arrangement of the foramina and the presence 

 of the alisphenoid canal as found in those genera which he 

 made to constitute the JSTimravidse is such as is found in primi- 

 tive forms. It is not unnatural that the higher forms should 

 have paralleled each other in the loss of the alisphenoid canal 

 and the disposition of the foramina, so that in Smilodon and 

 Felis we find the same conditions although the two genera 

 represent the most specialized forms of the phyla in which the 

 basi-cranial characters are known. The two subfamilies ex- 

 hibit a most remarkable parallelism in development. The 

 point of divergence from a common ancestor is quite removed 

 from the position by the most primitive of the well known 

 genera. Indeed it is not impossible that the Felidse may have 

 had a separate origin from the Creodonts, but our knowledge 

 of their early relationships is too meagre to justify any definite 

 conclusions on this point. As we know them the phyla are 

 distinct. 



The following key for determining the genera of the Felidae 

 is submitted. ^Elurotherium not being well known is con- 

 trasted with Dinictis, which it most resembles in the characters 

 known. Eusmilus, being known only from the lower denti- 

 tion, is contrasted with Hoplophoneus. 



I. Superior canines large and powerful, usually saber-shaped 

 with posterior and anterior denticulate borders. Inferior 

 canine not greatly exceeding the outer incisor. Mandible with 

 the symphysial portion separated from the lateral by an angle, 

 the anterior inferior border of the ramus with a flange or mak- 

 ing an obtuse angle with the symphysial portion. 



Mach^rodontln^e. 



A. Anterior inferior border of mandible with an obtuse angle. 



a. Superior sectorial without internal cusp. 



a. a. Superior canine recurved posterior border, not den- 



I ticulate. 



* 1. Dentition IfC|Pm|M| Archcelurus. 

 b.b. Superior canine recurved posterior border, denticulate. 



2. Dentition If C^ Pmf M£ JSlurogale. 

 ex. Superior canine spike shaped. 



3. Dentition If CiPmf M£ Nimravus. 



B. Anterior inferior border of mandible with a flange. 



b. Superior sectorial with internal cusp. 



d.d. Inferior sectorial with strong postero-internal cusp 

 and talon. 



4. Dentition ? If C|Pmf M-J ^Elurotherium. 



e.e. Inferior sectorial with small postero-internal cusp, 

 talon reduced. 



