CUEODOXTA. 3(51 



are decided ^joints of resemblance to the bears, but the cavum tympani is 

 even less expanded than in those animals. The characters of dentition are 

 more like those of the HycEnodontidce and Amhhjctofiichc than any other 

 group, and even the remarkable incisor-like inferior canines are approxi- 

 mated by the anteriorly directed canines of Hycenodon leptorliyndms Laiz. 

 et Par. 



The Mesonyx lanius was considerably larger than the If. obtusidens, 

 equjling the black bear (Urtius americanus) in size. It had a large head, 

 with a long, rather narrow, and truncate muzzle. The limbs were relatively 

 smaller, not exceeding those of the black bear in length and thickness. 

 The tail was long and slender as in the cats, while the claws were broad 

 and flat as in the beaver. 



Habits. The molar, cani>ie, and incisor teeth of my specimen, as well 

 as that of the Princeton fossil, are. much worn by use. This is especially 

 true of the canines of both, while the crowns of the molars of the Bitter 

 Creek specimen are almost entirely worn away. The same peculiarity is 

 to be observed in the specimens of the allied Amhlyctonus sinosus, which I 

 obtained in New Mexico.* It is probable that these species chewed hard 

 substances. The peculiar approach of the lower canines is a special modifi- 

 cation for peculiar habits, which I suspect to have been the devouring of 

 the turtles which so abounded on land and in the waters of the same period. 

 The slender symphysis could most readily be introduced into the shell, 

 while the lateral pressure of the upper canines with the lower, would be well 

 adapted for breaking the bony covering of those reptiles. The breaking of 

 these shells in the attempt to masticate their contents would produce the 

 unusual wear of the teeth observed. 



History. I originally placed this species in a genus distinct from the 

 M. ohtusidcns on the ground of a supposed difference in the number of molar 

 teeth. The Princeton specimen renders it extremely probable that the two 

 species are congeneric. 



The dental series is uninterrupted from the canine if, as I believe, 

 there is an alveolus for a simple premolar behind it. This I overlooked 



*Sec Report of Lieut. G. M. AVheeler, Expl. Siirv. W. of 100th Mer., 1 v., irt. ii, PI. xxxiii, 

 figs. 1-3 and 11. 



