226 TKOCEEDINGS OF THE NATIONAL MUSEUM vol. 85 



rations P4, 16 specimens, 10-13, mode 12, type 11. Cusps Mi, 

 7 specimens, 6-7:4, mode 7:4, type 6:4. 



Genus ECTYPODUS Matthew and Granger 



7ECTYPODUS GRANGERI.e new species 



Type.— U.S.N.M. no. 9801, left lower jaw with P4-M1. Collected 

 by A. C. SUberling.. 



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

 cene horizon. Crazy Mountain Field, Mont. 



Diagnosis. — Structurally similar to Ectypodus musculus but sig- 

 nificantly larger. Length : width ratio Mi larger and cusps Mj 

 more numerous than in any species referred to Ptilodus. P3 present. 

 Length P4 (mean of 4 specimens) 5.3. Length Mi (mean of 3 speci- 

 mens) 3.4. Ratio length P4 : length Mi (type) 1.56. Ratio length 

 Ml : width Mi (mean of 3 specimens) 2.4. Serrations P4, 4 speci- 

 mens, 13-14, mode and type 14. Cusps Mi, 3 specimens, 8:6-7, 

 mode and type 8:7. Apex of P4 nearly on a level with grinding 

 surface of Mi. 



7ECTYPODUS RUSSELLI.? new species 



Type.— U.S. ^.M. no. 9765, left lower jaw with P4-M2. Collected 

 by A. C. Silberling.. 



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

 cene horizon. Crazy Mountain Field, Mont. 



Diagnosis. — Similar to '^E. grangeri but slightly smaller, external 

 cusps of Ml more numerous, and P4 more elevated above Mi. P3 

 present. Also similar to E. cochranensis, but notch in anterior base of 

 P4 much more pronounced. Length P4 (mean of 3 specimens) 5 mm. 

 Length Mi (2 specimens) 2.9 mm. Ratio length P4 : length Mi 

 (2 specimens) 1.7. Ratio length Mi : width Mi (type) 2.4. Serra- 

 tions P4 (3 specimens) 13-15, type 14. Cusps Mi (2 specimens) 

 10-11:6, type 10:6. 



7ECTYPODUS SILBERUNGI.s new species 



Type. — U.S.N.M. no. 9798, left lower jaw with incisor and P4-M2. 

 Collected by A. C. Silberling. 



Horizon and locality. — Gidley Quarry, Fort Union, Middle Pale- 

 ocene horizon. Crazy Mountain Field, Mont. 



Diagnosis. — (Type specimen unique.) Similar to E. musculus but 

 smaller and more cusps on Mi. Size close to "^Ptilodus sinclairi, but 

 Ml significantly longer absolutely and relative to its width and with 

 more cusps. Length P4 3.3 mm. Length Mi 2.3 mm. Ratio length 

 P4: length Ml 1.4. Length Mi : width Mi 2.6. Serrations P4 12. 

 Cusps Ml 9:5 (or perhaps, counting rudiments, 10:6). Crest of P4 

 relatively low, 



« Named for Dr. Wnlter Granger for liis work on the Paleocene of North America and Asia. 



' Named for Dr. L. S. Russell for liis worlc on the I'askapoo. 



* Named for A. C. Silberling, who collected most of the mammals herein described. 



