Marsh Collection, Pedbody Museum. 287 



most of the teeth in situ. These remains indicate an animal 

 somewhat larger than Mesonyx uintensis of the Uppermost 

 Eocene stage, which has hitherto been considered the largest 

 Carnivore of the Eocene. The skull exceeds that of a full- 

 grown Grizzly Bear, but the body was not as large in propor- 

 tion. 



The principal generic characters have already been stated in 

 the foregoing analytical table. Those which distinguish it 

 most sharply from the contemporary Dromocyon and Mesonyx 

 are seen in the reduced number of superior premolars and the 

 presence of an entepicondylar foramen in the humerus. Addi- 

 tional characters of importance are : The absence of a super- 

 trochlear foramen of the humerus, the lack of complete molari- 

 form structure of the fourth superior premolar, together with 

 the absence of the third superior molar. I have provisionally 

 placed this form in the section having five toes on each foot, 

 largely on account of the unspecialized condition of the 

 humerus, which resembles that of Pachymna more closely than 

 Mesonyx or Dromocyon. The foot structure is unknown, but 

 we can readily believe that the toes were not so much reduced 

 as in the more specialized genera. 



The Skull. (Plate I.) — The muzzle appears to be propor- 

 tionally longer and wider than that of either Dromocyon or 

 Mesonyx. The nasals spread out posteriorly, as in these genera, 

 leaving only a narrow contact between frontal and maxillary. 

 This condition is associated with the large extra-orbital extent 

 of the lachrymal, which is spread out upon the side of the face, 

 as in all the Mesonychids. The orbit is relatively more pos- 

 terior than in Dromocyon or Mesonyx, and the lachrymal canal 

 is single, rather small, and placed within the rim of the orbit. 

 The pr em axillae are of moderate size, articulating freely with 

 the nasals above, but not extending backward to join the 

 frontals ; they terminate posteriorly just above the infraorbital 

 foramen, which is relatively large and issues above the middle 

 of the third premolar. The brain-case and posterior frontal 

 region are not well preserved, but there is evidence of a dis- 

 tinct postorbital process and a high sagittal crest. The palate 

 is long and rather narrow ; the opening for the posterior nares 

 is placed well behind the posterior termination of the tooth 

 line, at the thickened terminal border of the hard palate. 

 Behind this the narial groove is narrow and not very deep, 

 the opposite pterygoid plates approaching each other below in 

 such a manner as to leave a rather narrow opening. This is 

 similar to the arrangement seen in the skull of many species of 

 Hymnodon and is particularly noticeable in Mesonyx uintensis, 

 as figured by Osborn.* The incisive foramina, or anterior 



*Bull. Amer. Mus. Nat. Hist., 1894. p. 80, 



