1880.1 * J . [Cope. 



Arctocyonid^. 



Premolars f ; the first inferior one-rooted ; the last in- 

 ferior well developed Arctocyon Blv. 



Premolars below, 4, the first two-rooted, the last true 



molar much reduced Hyodecten* Cope. 



Premolars below, 3, first two-rooted ; true molars nor- 

 mal Heterohorus\ Cope. 



MlACID^. 



Inferior tubercular molars two, premolars four Miacis Cope. 



Inferior tubercular molars one, premolars four DidymicUs Cope. 



OXY^NID^. 



I. Inferior molars without internal tubercles. 

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



II. Inferior molars with internal cusps. 



Molars, f I ; two last inferior molars tubercular-sec- 



torial Oxycena Cope. 



Premolars | ; three last inferior molars tubercular-sec- 



torial ; the fourth superior with a conic cusp and 



heel externally Stypoloplms Cope. 



Premolars!; three last inferior molars tubercular-sec- 



torial ; fourth superior premolar with a simple blade 



externally. , Proviverra Riitim. 



Amblyctonid^. 



Fourth inferior premolar with a broad heel supporting 



tubercles Amhlyctonus Cope. 



Dental formula below, 3, 1, 3, 3. Fourth inferior pre- 

 molar with a cutting edge on the lieel Palceonyctis Blv. 



Mesonychiid^. 



Inferior molars seven Mesonyx Cope. 



Inferior molars five Patriofells Leidj^. 



Of the preceding genera it may be remarked, that the structure of the 

 feet of Pterodon being unknown, it may be found hereafter to be neces- 

 sary to remove it from the Oxymnidm, although I do not anticipate that 

 such a course will be necessary. Palceonyctis is only known by tlie man- 

 dibular dentition, which is very near to that of Amblyctonus. So also it 

 is not certain, but only probable, that Patriofelis belongs to the Mesony- 



* Type Arctocyon gervaisH Lemoine, Oss. Foss. des Eiivii". de Reims, 1878, p. 8. 

 t Type Arctocyon duelii Lemoine, 1. c., p. 9. 



