100 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



Horizon and locality. — Gidiey Quarry, Fort Union, Middle Paleo- 

 cene horizon. Crazy Mountain Field, Mont. 



Diagnosis. — Length P4, type and mean of three, 5.0. Length Mi, 

 type and referred specimen, 2.9. Ratio length P4: length Mi, type 

 and referred specimen, 1.7. Length Miiwidth Mi, type 2.4, referred 

 specimen 2.6. Serrations P4, type 14, others one 15, one 13. Cusps Mi, 

 type 10:6, referred 11:6. Cusps M2, type and referred specimen 5:2. 

 Crest of P4 elevated well above M^ 



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Figure 10.— Edypodus and Pared y pod u,s, comparative outline drawings of lower dentitions: a, E. grangerl 

 Simpson, U.S.N.M. no. 9S01; 6, E. russeUi Simpson, U.S.N.M. no. 9765; c, E. sUbertingi Simpson, 

 U.S.N.M. no. 9798; d, P. jepseni Simpson, U.S.N.M. no. 9769. Crown and external views, left lower 

 jaws. Three times natural size. 



Remarks. — This species considerably resembles the preceding one, 

 and I was at first inclined to consider its smaller size as due only to 

 variatio», as it is well within the possible size limits. That would, 

 however, make the range in Mi external cusp number for the com- 

 bined species twice as great as has been demonstrated for any known 

 species of this or allied genera, even in much larger samples, and the 

 probability is very greatly against this occurring in a single species 

 and against the association of larger cusp number with smaller size 

 being due to accidents of sampling. It is possible also, although 

 less clear, that association with a slightly larger length P4: length Mj 

 ratio is significant. The added character of a more elevated P4 

 makes the specific distinction practically certain. 



P4 of this species very closely resembles that of Edypodus coch- 

 ranensis. However: (a) It here has a definitely larger notch for 

 P3, (b) the localities are well separated, (c) the ages are distinctly 



