362 THE WASATCH FAUNA. 



when first describing the species, and hence gave the molars as 6 instead 

 of 7. 



The typical specimen was found by myself on a terrace of the Mam- 

 moth Buttes, near South Bitter Creek, Wyoming, in the beds of the Wash- 

 akie basin. A portion of the bones had fallen a few feet from a remaining 

 mass of the softer bed, where I soon found the rest of the specimen in place. 

 The skull and anterior foot were taken out from close juxtaposition. 



Mesonyx ossifragus Cope. 



Plates XXVIII a, Fig. 1 ; XXVIII b; XXVm c; XXVIII d ; f XXIV e, figs. 14-19. 



American N.atnralist, 1881, p. 1019, December. Proceedings Am. Philos. Soc, December, 1881, p. 165. 

 Pachtiana ossi/raga Cope, Report Vert. Fossils New Mexico, U. S. Geog. Snrv. W. of 100th Mer., p. 

 13, 1874. Id., Ann. Report Chief of Engineers, 1874. Report Lieut. Wheeler, p. 12.">. Report 

 Capt. Wlieclor, U. S. G. G. Surv. W. of 100th Mer. iv, ii, p. 94, 1877, pi. .xxxix, fig. 10. 



I was so fortunate as to receive from Mr. Wortman the greater part of 

 a skull of this species, together with some bones of the limbs, belonging to 

 one individual. These were mingled in great confusion with tlie bones of 

 two individuals of PJienacados, which I was able to distinguish through the 

 fortunate possession of a complete skeleton of the P. primcevus. Besides 

 this individual, Mr. Wortman obtained jaws and some of the bones of three 

 individuals from the Big Horn basin. 



M. ossifragus was the largest Creodont of the Eocene, equaling the 

 largest grizzly bear in the size of its skull. In a cranium with lower jaw 

 and almost complete dentition, the length to the preraaxillary border from 

 the postglenoid crest is M. .365 ; the largest Ursus horribilis in my collec- 

 tion gives .270 for the same length. This specimen has the dental formula 



I. -; C. ; P-m. -; M. -. The claws have the flattened form which I dis- 

 2 1 4 3 



covered in 3£. lanins, and the proximal phalanges have much the shape of 



those of a Perissodactyle. Tlie astraglus has much the character of the 



animals of that order, and has the distal facets as I originally detected 



them in the M. obtusidens The form of this bone is shorter and wider 



than in the latter species. 



The skull already mentioned lacks the brain case and basicranial axis, 



embracing the muzzle, zygomata, pterygoid region, and lower jaw, with 



