Vol. 5] 



Merriam. — John Day Camivora, 



45 



groups Archaelurus and Nimravus beyond the type materia]. It 

 should be stated further that a somewhat similar mingling of 

 characters of these genera is encountered in a study of the struc- 

 ture of the skull, limbs, and vertebrae. As far as is known, 

 nearly all the supposed diagnostic characters seem to be variable 

 and untrustworthy, excepting possibly the form of the massateric 

 fossa, and it is doubtful whether more than specific value at- 

 taches to this feature. The group as a whole seems to show much 

 individual variation, and under these circumstances a thoroughly 

 satisfactory arrangement of the species and genera can be accom- 

 plished only by the study of much larger collections than are now 

 available. Cope's collection seems to have contained in the types 

 of A. clebilis and N. gomphodus two rather extreme variants. 

 Neither of these extremes has been met outside of the type col- 

 lection. Although the larger part of the known material is not 

 included in Cope's collections, all of the specimens range between 

 the limits of these two forms. 



Collectively the forms in the Nimrav us- Archaelurus group 

 represent a fairly distinct feline type. They are characterized 

 in skull and dentition by the absence of a prominent flange on 

 the antero-inferior angle of the mandible; a tedency toward full 

 representation of the premolars; absence of deuterocone on P*, 

 of pr^fcocone on M\ and of metaconid on M x ; incomplete develop- 

 ment of the anterior cutting edge on the superior canines ; the 

 presence of a small M 2 and of a peculiar exostosis on the external 

 alveolar margin adjacent to it; and the slight inferior projection 

 of the posttympanic process and of the root of the zygomatic 

 process of the squamosal. This group corresponds in rank to 

 the average genus and, unless finisher additions to the available 

 material should bring out more definite distinguishing characters, 

 the later name, Archaelurus, will probably be ultimately elim- 

 inated. 



As has been recognized particularly by Adams/ 14 the members 

 of the Nimravus- Archaelurus group show strong resemblances in 

 dental and cranial characters to Ailurictis of the European Olig- 

 ocene and, as indicated below (p. 50) under the discussion of the 

 extremities, this similarity extends also to the limb structure. 



34 G. I. Adams. Extinct Felidae., Am. Jour. Sc., 1897, Vol. 154, p. 146. 



