BUNOTHERIA. 



CREODONTA. 



HEMIPSALODON, Cope. 



This genus belongs to the OxyaenidEe, and is the only one of that family that has been 

 found in beds higher than the Bridger Eocene. The only known species is the largest of 

 the Creodonta. and the jaw from which it is known is more robust than that of any exist- 

 ing carnivore. Its dimensions are about those of the Aclianodon insolens of the Bridger 

 beds. The genus Hemipsalodon differs from the others of the family in the presence in 

 the lower jaw of the full dental series of four premolars and three true molars without 

 diastema behind the canine. Incisors three. The only crown perfectly preserved is the 

 last true molar. It is of the type of Oxyasna, but has probably no internal tubercle or 

 rnetaconule ; (specimen worn at that point). It has a heel more or less cutting. 



This remarkable genus resembles, so far as the characters preserved permit us to 

 judge, the Stypolophus of the Eocenes, which embraces numerous species, none of which 

 exceeded a red fox in size. It is, however, most nearly related to Pterodon, with which 

 Schlosser believes it to be identical. That possesses but three inferior premolars, but 

 the value of this character in this case is not yet certainly known. If no other character 

 distinguish Hemipsalodon but the four inferior premolars, the Pterodon quercyi of Filhol, 

 from the French phosporites, must be placed in it. The blade of the last inferior molar is 

 more oblique to the long axis of the jaw than is represented to be the case in the Pterodon 

 dasyuroides, making an angle of 30° with it, while the edge of the heel is slightly oblique 

 to it in the opposite direction. This may indicate some peculiarity in the superior molar, ■ 

 or it may be but a specific character. 



Hemipsalodon grandis, Cope. 



American Naturalist, 18S5, p. 1G3 ; Annual Report of the Geol. and Nat. History Survey of Canada, 1SS5, 

 Appendix C, p. 2. 



The species is characterized by the deep compressed form of the ramus, and the long 

 symphysis. The incisor teeth are crowded, the first and third being external and close 

 together, and the second internal in position. The canine tooth is of enormous size, and 

 is directed upwards. The section of the summit of the root is a wide oval without 

 angles. The premolars are all two-rooted, except the fourth. The first is longer than the 

 first true molar. The true molars increase in size posteriorly. The third is very robust, 

 and has elevated cusps, with a sub-triangular section, the median exceeding the anterior. 

 The sectorial edges are very steep, forming together a Y. The heel is quite short, and has 

 a cutting keel, which is the summit of the external face, and is nearly median. The coro- 

 noid process rises at a A r ery short distance posterior to it. The masseteric fossa does not 

 extend downwards to the inferior edge of the ramus. The latter is inflected on the inner 

 side as far posterior as below the middle of the coronoid process, where it is broken off. 



Length of the dental series, M. .212 ; of true molars, .085 ; of premolars, .108 ; diameters 

 of last true molar : anteroposterior .034, transverse .021 ; do. of canine at base : anteropos- 

 terior .040, transverse 029. Depth of ramus at M. 3, .086 ; length of symphysis, .131. 



This species was the largest flesh-eater of the epoch of the "White River beds, and the 

 size of its canine teeth proves it to have been a dangerous animal. Its molars are 

 interesting on account of their illustrating a primitive form of a sectorial tooth. 



