102 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



Among other species, it most closely resembles Ectypodus musculus, 

 but aside from the different horizon and locality it differs in being 

 somewhat, perhaps significantly, smaller and in having more cusps 

 on Ml, as well as other minor distinctions that may prove also to be 

 significant when a larger sample permits their evaluation. 



Measurements of the type other than those given above: Width 

 Ml, 0.9; length Mo, 1.2; width Ms, 1.0; ratio length Mi '.length Ms, 

 1.9; cusps Ma, ?o:3. 



7ECTYPODUS species 



U.S.N.M. no. 9772 includes three unassociated last upper premolars, 

 one broken, from the Gidley Quarry. They have one complete row 

 of 11 cuspules, or serrations, and a rudimentary anteroexternal basal 

 row of 2 cusps, both strong and distinct, the more posterior larger 

 and opposite the third or fourth cusp of the main row. These teeth 

 suggest Ectypodus musculus, but the elevation of the posterior end of 

 the main crest is less than in that species, and the apex is not on the 

 most posterior cuspule but on the fourth or fifth from the posterior 

 end. Neoliotomus conventus is inadequately known, but apparently 

 these specimens are less symmetrical in lateral contour. Size and 

 cusp number surely distinguish the species from any comparable form, 

 and the generic reference is doubtful. The lengths of the two more 

 complete teeth are 4.8 and 4.5 mm. 



These probably represent the upper dentition of one of the species 

 here named from lower jaws, and by inference somewhat more prob- 

 ably one referred to ?Ectypodus, but the association cannot be estab- 

 lished. From the ratio length P4: length P* in Ectypodus musculus 

 (1.48), the lower P4 should be 6.7-7.1 mm in length, about as in 

 fPtilodus douglassi, but the latter has no characters suggesting 

 Ectypodus. fEctypodus grangeri may be based on the corresponding 

 lower teeth, but it seems somewhat too small. 



Genus PARECTYPODUS Jepsen, 1930 



7PARECTYPODUS JEPSENI Simpson 

 FiGXJRE 10, d 



? Par ectypodus jepseni Simpson, 1935d, p. 227. 



Tl/pe.— U.S.N.M. no. 9769, left lower jaw with P4-M1. Collected 

 by A. C. Silberling. 



Horizon and locality. — Gidley Quarry, Fort Union No. 2, Crazy 

 Mountain Field, Mont. 



Diagnosis. — (Only one specimen.) Length P4, 4.3. Length Mi, 

 3.1. Ratio length P4: length Mi 1.4. Length Mi: width Mi, 2.2. 

 Serrations P4, 11. Cusps Mj, 7:6. P4 long and low. No notch for P3. 



Remarks. — This can be compared only with the later Parectypodus 

 simpsoni. Its longer Mi, lower length P4:length Mi ratio, smaller 



