NOTES ON THE CANIDJE OF THE WHITE RIVER OLIGOCENE. 660 



The mandible differs considerably in the various species, though the comparison 

 between them can as yet be but partially made, for the only specimen known to me in 

 which the angle and coronoid process are preserved, is that figured by Leidy (I. c, PI. I, 

 Fig. 2), which belongs to D. vetus. In f D. dodgei (PL XIX, Figs. 6, 7.) the horizontal 

 portion of the mandible is thick, heavy and relatively short; the inferior border is very 

 far from straight, rising beneath the masseteric fossa almost to the level of the molars and 

 descending forward from this point in a bold, sweeping curve, quite as in the modern 

 Canis aureus ; the masseteric fossa is very deep and its ventral border forms a prominent 

 ridge, distinct from the lower border of the jaw ; the symphysis is short and the chin 

 abruptly rounded and steeply inclined. 



In D. vetus the horizontal ramus is of an entirely different shape (see PL XIX, 

 Fig. 5) being longer, more compressed and slender and with a decidedly straighter 

 ventral border ; the symphysis is longer and the chin more gently rounded, rising more 

 gradually from the inferior margin of the ramus. The masseteric fossa is quite deeply 

 impressed, though less so than in f D. dodgei, and is very large, extending far up upon 

 the ascending ramus. The angle is a stout hook, which is less elevated above the general 

 level of the horizontal ramus than in modern wolves or foxes. The condyle also has a 

 low position, below the level of the molars, while in recent species the condyle is raised 

 above the molars, and in some species very much so. The ascending ramus has great 

 antero-posterior extent, by which the condyle is removed far back of the last molar. 

 This is a primitive feature which recurs in most creodonts and is evidently correlated 

 with the characteristic elongation of the cranium and zygomatic arches. The coronoid 

 process is high and wide, and has a bluntly rounded end ; it inclines much more strongly 

 backward than in Canis and has a much more concave posterior border. The condyle 

 resembles that of the recent clogs, but is set upon a more distinct neck, is more extended 

 transversely, and is less cylindrical in shape, tapering more toward the outer end. 



In D. hartshornianus the mandible, so far as it is preserved in the various speci- 

 mens, resembles that of D. vetus, save that the horizontal ramus is somewhat shallower 

 and more slender. 



The Brain. Very little can be said concerning the brain, since no complete cast of 

 the cranial cavity is available for study. The general shape and development of the 

 brain are, however, indicated in the specimen of D. hartshornianus already described 

 (PL XIX, Fig. 1). Its j;>roportions are very different from those found in existing 

 members of the family, a difference which may be briefly stated as largely consisting in 

 the much greater relative size of the cerebral hemispheres and smaller size of the olfac- 

 tory lobes in the modern species. In Daphamus the brain is narrow and tapers 

 rapidly toward the anterior end ; the cerebellum and medulla oblongata are long, the 



A. P. S. — VOL. XIX. 2 Q. 



