82 



BULLETIN" 16 9, UNITED STATES NATIONAL MUSEUM 



Of the eight definable Fort Union species, only one, Ptilodus mon- 

 tanus, can be placed with certainty as to genus. This is well known, 

 from the entire dentition, and is so close to the genotype of Ptilodus 

 that it certainly belongs to that genus. The species jepseni is excluded 

 from all named genera but Parectypodus and Eucosmodon by the 

 absence of a notch for P3. It does not resemble the type species of 

 either of these genera very closely in the known parts (P4 and Mi), but 

 it is somewhat closer to Parectypodus simpsoni and may be placed, 

 very tentatively, in the same genus. Three species, silberlingi, 

 russelli, and grangeri, have what seem to be the most distinctive lower 

 jaw characters of the type of Edypodus, large length : width ratio of 

 Ml (2.4 to 2.6 in these species, 2.5 in E. musculus), and large cusp 

 number of Mi (total 14-17 in these species, 14 in E. musculus, typi- 

 cally 9-10 in Ptilodus). They are therefore tentatively referred to 

 Edypodus, although it is not probable that all belong to one genus or 

 certain that any belongs to this genus. This leaves three species, 

 sinclairi, gidleyi, and douglassi, which are tentatively placed in Ptilodus. 

 The assignment is very uncertain in all three cases, and especially so for 

 sinclairi, which, I suspect, may prove to represent a new genus when 

 upper teeth are known, but no more probable position can be given 

 them at present. 



As previously mentioned, with this material it is now impossible to 

 recognize genera properlj^, and were it not for the requirement that a 

 species be referred to some genus it would be m.ore satisfactory at pres- 

 ent to consider all eight species (or the seven other than montanus) 

 simply as species at large in the family Ptilodontidae. 



Table 9. — Comparison of lower dentition of I4 species of Ptilodontidae 



Species 



IPtUodus sindain 



f Edypodus silberlingi 



1 Par edypodus jepseni 



lEdypodus russelli 



? Edypodus grangeri 



T Ptilodus gidleyi 



t Ptilodus douglassi- 



Ptilodus montanus 



Ptilodus mediaecus 



Ptilodus irovessartianus 



Paredypodus simpsoni 



Paredypodus tardus 



Edypodus musculus 



Edypodus cochranensis 



Length 

 Pi 



Mm 

 3.1 

 3.3 

 4.3 

 5.0 



5.3 

 6.0 

 6.6 

 8.0 

 8.3 

 5.9 

 4.2 

 3.0 

 4.0 

 4.9 



Length 



Ml 



Mm 

 1.9 

 2.3 

 3.1 

 2.9 



3.4 

 ca2.5 

 3.7 

 3.4 

 3.5 

 3.1 

 2.3 

 1.9 

 2.5 



LP4 



LMi 



1.6 

 1.4 

 1.4 

 1.7 



1.5 

 ca2. 4 

 1.8 

 2.3 

 2.3 

 1.9 

 2.0 

 1.6 

 1.6 



LMi 



WMi 



2.2 

 2.6 

 2.2 

 2.5 



2.2 

 2.0 

 2.0 

 1.9 

 2.1 

 2.4 

 2.5 



Serra- 

 tions 

 Pi 



11.4 

 12.0 

 11.0 

 14.0 



13.7 



14.3 



13.0 



13.8 



12.2 



13.8 



14 



10 



13 



14 



Cusps 

 Ml 



6.6:4 

 9.5:5.5 



7:6 

 10.5:6.0 



LMi 

 LM2 



1.9 

 1.9 



1.8 

 1.4 

 1.4 

 1.8 



Remarks 



No notch for P3. 



Notch for P3 more 

 pronounced 

 than in E. 

 cochranensis. 



No notch for Pj. 

 No notch for Pj. 



