342 GEOLOGICAL SURVEY OF THE TERRITORIES. 



covered in the iniocene tertiary deposits of the Mauvaises Terres of White 

 Biver, Dakota. They are as follows : 



Amphicyon vetus. — A species about the size of the living prairie wolf 

 (Cants latrans,) indicated by the mutilated cranium and fragments of 

 jaws, with teeth ; discovered by Dr. John Evans and Professsor Hayden. 



Ampliicyon gracilis. — A small species, less in size than any of the ex- 

 isting American foxes. It is indicated by fragments of jaws, with teeth, 

 and the facial portion of a skull of several individuals ; ail discovered by 

 Professor Hayden. 



HYJENODONTID^E 



Is the name given to an extinct and remarkable family of animals, 

 exhibiting a relationship to the canine family on one hand, and the fe- 

 line family on the other, together with ties to others. 



HY^NODON. 



One of the most remarkable extinct genera of carnivorous animals is 

 that to which the above name has been given. It belongs to no exist- 

 ing family, and, indeed, is so peculiar as to have become the type of an 

 independent family. In anatomical character it partakes of those of 

 the wolf, the tiger, the hyena, and the weasel, the raccoon, and the 

 opossum. Originally discovered in Prance, the remains of live or six 

 species have been obtained from the lower miocene and upper eocene 

 formations of that country. Three American species are indicated by 

 fossil remains obtained in the lower miocene tertiary beds of the Mau- 

 vaises Terres of White Biver, by Dr. John Evans, Dr. Benjamin Shu- 

 mard, Professor Hayden, and Mr. Meek. These species are as follows : 



Hycenodon horridus. — The largest known species, and one of the most 

 sanguinary of terrestrial mammals that has ever existed. Cotempora- 

 neous with a multitude of herbivorous animals, many of which were 

 gregarious in extensive herds, it was no doubt a fearful scourge to 

 them. It is indicated by the greater portions of three skulls, together 

 with fragments of jaws and teeth of other individuals. The size of 

 the animal was about equal to that of the largest black bears. The 

 specimens of jaws and teeth discovered have afforded us a view of the 

 entire dentition of the animal, which is truly formidable. Besides the 

 powerful canine teeth, the series of molars affords the unusual exhibi- 

 tion of three teeth, constructed nearly after the model of the single sec- 

 torial tooth of other carnivorous mammals, though the last one alone 

 reaches the full development of the corresponding tooth in the latter. 



The true sectorial molars of hysenodon, the last of the series of teeth, 

 are constructed like those of the lion and tiger. These teeth, the 

 broadest and strongest of all, combine the mechanism of the wedge 

 and the scissors, and are admirably adapted to cutting animal tissues, 

 including bones. 



The large temporal fossse occupying the sides of the skull, and sepa- 

 rated only by a long and high median ridge, sufficiently prove the 

 great power of the muscles which operated on the long levers of the 

 lower jaw. Certainly no other animal which lived cotemporaneously 

 with this formidable creature could have resisted its power. The skull 

 of the species measures about a foot in length. 



Hycenodon crucians. — This is the name given to a species not much 

 exceeding in size the red fox (Canis fulvus.J A half dozen imperfect 

 skulls of the animal, together with fragments of jaws and teeth, and 

 other bones, have been discovered. Though small, compared with the 



