1892.] NATURAL SCIENCES OF PHILADELPHIA. 321 



and Wind River, and M. brevirostris only in the latter beds. A 

 very doubtful species is the ? M. (? Ampliicyoii) vulpinus Scott and 

 Osborn, from the Uinta Eocene, which is too imperfectly known for 

 certain reference. 



VIVERRAVUSi Marsh. 



This genus is very inadequately known, but appears to differ from 

 the other members of the family in the mandibular formula : P3 

 Mf- M2 and 3 are tubercular, but the trigonid retains all three cusps and 

 rises considerably above the level of the talon. The premolars are 

 much compressed and the mandible long and slender. 



Three species : F. gracilis Marsh : ? V. nitidus Marsh, V. (Limno- 

 cyoii) riparius Marsh : Bridger. 



THIN0CY0N2 Marsh. 



Not improbably this genus is identical with the preceding one. 

 The mandibular formula is given as : I^ Cx Ps M, ; m^ and^ are 

 tubercular and the angle of the mandible is said to be reflected. 



One species : T. velox Marsh, Bridger. 



Genera Incert^ Sedis. 



Under this head will be discussed a number of forms which have 

 been referred to the Creodonta, but the nature of which is very pro- 

 blematical. 



MIOCLiENUSs Cope. 



In his latest paper on the Puerco fauna, Cope refers to this genus 

 no less than twenty-six species, which range in size from that of a 

 black bear to that of a squirrel. The presence in one horizon and 

 locality of so many species of a single genus and with so great a 

 range of size, is, on the face of it, highly improbable, and I believe 

 the genus, as at present constituted, to be an unnatural one. For 

 structural reasons, I have subdivided the group into many genera, 

 some of which have been described above, and others remain to be 

 mentioned. The name Mioclcemis should be restricted to those forms 

 which agree with the type species, M. turgidus, in the extremely 

 broad, low and massive premolars, which equal or exceed the molars 

 in size ; these are : M. turgidus Cope, M. opisthacus Cope, M. zitte- 



1 Amer. Journ. Sci. and Arts, 2nd Ser., Vol. IV, 1872, p. 127. 



2 Loc. cit., p. 204. 



3 Amer. Naturalist, 1881, p. 830. 



22 



