348 THE WASATCH AJsD BIflDGEK FAHNJS. 



MESONYX Cope. 



Paleontological Bullotin No. 1, p. 1, July ^J, 187a. Proceed. Auicr. Pliilos. Soc, 1872, p. 460. Ibid., 1873, 

 p. 198. Tlio Flat-C'liin-e<l Carnivora of tbo Eoccueof Wyoiuing, .\])ril 19, 1873, p. 1. t Synoplo- 

 therium Cope. Pal. Bull. No. fi, p. 1, Aug. 20, lb7->. Proceed. Aiii.r. I'liiloa. Soe., 1872, p. 48:1. 

 Flat-Clawed Caruivora, etc., p. 5, plates I and 2. Proceed. Amer. Pliilos. Soc., 1873, p. 203. 

 Annual Report U. S. Geog. Geol. Surv. Terrs., Hayden, 1872 (187:t), pp. 550, ."VVJ, plates 5, 6. 



This genus is known from the dentition of the lower jaw and part of 

 that of the upper, and from many parts of the skeleton. The superior 

 molar teeth are yet unknown. Of the known parts of the skeleton the 

 anterior limbs are derived from the M. lanius, while the vertebrae and poste- 

 rior limbs are those of the M. obtmidens. As I have hitherto placed these 

 species in different genera, I must explain my reasons for uniting them in 

 Mesonyx. The two species were obtained from different localities, the M. 

 lanius from the Washakie, and the M. obtusidens from the Bridger basins. 

 It is not certain that these beds belong to exactly the same horizon. 

 Through the kindness of Professor Guyot, I have been able to examine 

 the lower jaw and teeth, with some other portions, of a species related to M. 

 lanius, if not the same, from the Bridger basin. Tliis specimen contains the 

 molar teeth characteristic of M. obtusidens ; the corresponding ones being 

 worn down by attrition in the type specimen of M. lanius. 



3 1 4 ? 



Dentition : I. = ; C. - ; Pm. - ; M. ~. The space between the inferior 



canines is so narrow that it is probable that the incisors were wanting or 

 reduced in number. The external superior incisor conical and larger than 

 the others. Superior canines vertical; inferior canines subhorizontal. First 

 inferior premolar one-rooted. Premolars from the third similar to the 

 molars, consisting of a posterior median blade, an anteromedian conic 

 cusp, and an anterior basal tubercle. The true molars diminish in size pos- 

 teriorly, but their composition is identical with that of the first, so far as 

 determinable. 



The cranium of the M. lanius is fractured above. There remain the 

 squamosal and periotic bones, occiptal condyles, malar and part of maxillary, 

 both premaxillaries and the greater part of both mandibular rami Tlio 

 squamosal process of the zygoma is produced inferiorly far below the audi- 

 tory meatus, even further than in the bears. Itspro.ximal portion includes, 



