552 GEOLOGICAL SURVEY OF THE TERRITORIES. 



donbt belong to tlie same niiiinal. It is evident that they differ in 

 character iioni those of niost existing Carnivora. The penultimate 

 phalanges agree with them in the depressed forni of their proximal ar- 

 ticular faces, wanting entirely the triangular form so characteristic of 

 Carnivora^ especially of the cats and dogs. The short, flat shaft of the 

 same is almost equally peculiar. 



The craninm is fragmentary. The malar bone of the right side is 

 similar in position and form to that of the Canidcc., especially in the 

 presence of a weak angle only, to mark the posterior border of the orbit. 

 It has a much less expanded union with the maxillary than in these 

 animals, and is proximally shallower, thicker, and more prominent. Its 

 jiosterior portion is more plate-like. 



There are numerous teeth ])reserved, but separate from the skull, and 

 mostly mandibular. The inferior canine is stout especially in the root, 

 which is a flat oval in section. The crown is but little curved, slightly 

 comi)ressed, and without edge or groove. The premolars graduate into 

 tl»e molars, so that the line of distinction is not easily drawn. The 

 first premolar has a single root; the crown is slightly conic, with a 

 small tubercle at the base behind. This tubercle increases in size on the 

 premolars 2 and 3, and becomes on the true molars a longitudinal 

 cutting edge extending along the axis of the crown, not much elevated 

 above a wide base. It occupies half the length of the crown in the 

 larger molars, and is preceded by an elevated conic cusp. In front of 

 the base of this, a small conic tubercle ]>rojects forwards, which appeared 

 as a rudiment on the third premolar. The number of mandibular teeth 

 would appear to be, P. M. 3, M. 4. Ko portions certainly referable to 

 the superior molars were found. 



Conclusion. In summing up, it may be accepted as a result of the 

 al;>ove analysis that the genus Mesonyx represents a family of Carnivora 

 digitigrada, distinct from any now living on the globe. The form of the 

 astragalus renders it probable that the inner toe is wanting orrudimen- 

 tal, and that there were four digits on the hind foot. The foot was also 

 short, and the claws flat, and altogether without prehensile use, but 

 rather adapted for aquatic lite. The number of molars exceals that in 

 any recent terrestrial family oi Carnivora except the ProtcUda, and their 

 sectorial form allies it at once to the extinct Hycenodontida. To this 

 family the genus Mcsouyx may possibly be at present referred. Amongre- 

 cent families it approaches nearest the Canido'jlmt has structires borrow- 

 ed from others, while its numerous molars coiistitute a point, of greater 

 generalization than any. Although sectorials, this char;cter is not 

 nearly so marked as in the existing Carnivora^ the cutting edge being 

 obtuse and occupying half the crown only, while theelevatec cone occu- 

 I)ying the remainder distinguishes the genus from these andfrovn Hyw- 

 nodon also. The lobe corresponding to this cone is i^receded ir Hyenodon 

 by a cutting edge, in Mesonyx by a tubercle. 



Mesonyx obtusidens. Cope. 



Proceedings American Philosophical Soc, 1872, 460, (July 29.) 



This species was as large as our largest wolves. While the proporti)us 

 of the limbs were not very ditferent, the body was rather more slenler 

 behind. The orbit was smaller, and the cheek bone more prominait 

 than in those animals. The long tail added to the general resembhme 

 to the dogs. The measurements are as follows : 



