Cope.] iOO [Dec. 16, 



II. One or more superior molars, with the external heel produced into 

 a blade. 



a. Molars 4—3 ; three last inferior tubercular sectorial. 



Premolars robust, conic Quercitherium Filh. 



Premolars compressed ; the fourth superior with a conic cusp and heel 



externally Stypolophm Cope. 



Premolars compressed ; fourth superior with a simple blade externally. . . 



Provherra Riitim. 



OXY^NID^. 



I. Inferior molars without internal tubercles. 



Molars, f | ; three sectorials in the lower jaw Pterodon Blv. 



II. Inferior molars with internal cusps. 



a. Posterior heel of one or more superior molars .elongate and trench- 

 ant. 

 Last inferior molar truly sectorial, without internal tubercle ; second, 



tubercular-sectorial Protopsalis Cope. 



Molars, ^ | ; two last inferior molars tubercular-sectorial . . . Oxycena Cope. 



Amblyctonid^. 

 Fourth inferior premolar with a broad heel supporting tubercles ; an 



anterior and no internal tubercles Ainblydonus Cope. 



Inferior molars with tubercular heel, an anterior and an internal tubercle. 



Pei'ijytychus Cope. 

 Dental formula below, 3, 1, 3, 3. Fourth inferior premolar with a cutting 



edge on the heel ; both internal and anterior tubercles 



Palceonyctis Blv. 

 Mesonychid^. 



a. Inferior molars seven ; 



Cones of inferior and superior molars simple Mesonyx. 



Cones of last two inferior molars with lateral cusps Dissacus. 



aa. Inferior molars ? six. 

 Internal lobes of penultimate superior molar v- shaped SarcotJiravstes. 



aa. Inferior molars five. 

 Inferior molars with strong anterior lobe Patriofelis* 



MlACIS CANAVUS CopC. 



Bulletin U. S. Geol. Survey, Terrs., 1881, p. 189. One mandible. 



MlACIS BREVIROSTRIS CopC, loC. cit. p. 190. 



Parts of four mandibles. 



DiDYMICTIS DAWKINSIANUS Cope, 1. C, p. 191. 



Six mandibular rami more or less complete. 



Individuals of the genus Didymictis are abundant in the Wasatch beds 



* Of uncei'tain refei'ence to this family. 



