THE MAMMALIA OF THE I>EEP EIVER BEDS. 



75 



cal data must be applied with great caution in discussing questions of skull morphol- 

 ogy. For the same reason, the sagittal crest is relatively less developed in very small 

 forms, as is exemplified in the small species of Cynodictis from the White River and 

 John Day, and in the least of these, C. (Galecynus) lemur, a lyrate area is formed, 

 the most ancient known cynoid in which it occurs. A sagittal area also occurs in 

 the "White River insectivores, Leptictis and Ictops, but it is worthy of note that it is 

 not marked in the older species of the latter, from the base of the Bridger. 



There are equally good reasons for regarding the lobate mandible which is found 

 in many of the recent Canidce as a secondary modification. It not only is absent in 

 all Miocene members of the family and all known creodonts, but, so far as I can 

 ascertain, it occurs only in those recent species in which the mandibular condyle is 

 much elevated above the level of the molars, and this is by no means a primitive 

 character. 



The following table will serve to display the relationships of the various Ameri- 

 can genera of the cynoid stem, so far as the available material renders this possible : 



Loup Fork, 



f Canis, JElurodon. 



John Day, 



"White River, 



Uinta. 



Cynodesmus, Temnocyon, Cynodictis. 



Dapliamus, 



Cynodictis. 



Bridger, 



3Kacis. 



CA^IS. 



? Canis anceps Scott. 



Amer. Nalurali&t, 1893, p. 660. 



A small fragment of mandible, containing the last premolar, first and second 

 molars, is provisionally referred to this genus. It agrees well with Cope's descrip- 

 tion of Canis brachypus from the Loup Fork (ISTo. 4, p. 389), except for its inferior 

 size and relatively more slender mandibular ramus. The inferior sectorial is nearly 

 as long as in that species, in the proportion of 17 to 19, but the depth of the jaw 

 beneath that tooth is much less, as 21 to 30. Possibly the species should be referred 

 to Cynodesmus, but several minute details point rather to Canis. 



