FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 99 



Genus ECTYPODUS Matthew and Granger, 1321 



7ECTYPODUS GRANGERI Simpson 



Figure 10, a 

 lEctypodus grangeri Simpson, 1935d, p. 226. 



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

 by A. C. Silberling. 



Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 

 horizon, Crazy Mountain Field, Mont. 



Diagnosis. — Length P4, type and mean of four specimens, 5.3. 

 Length Mi, type and mean of three specimens, 3.4. Ratio length P4: 

 length Ml, type 1.56, referred specimen 1.53. Length Mi: width Mi, 

 type 2.6, mean of three specimens, 2.4. Serrations P4, tj^pe 14, other 

 specimens, two 14, one 13. Cusps Mi, type, 8:7, other specimens one 

 8:7, one 8:6. Apex of P4 nearly on a level with grinding surface of 

 Ml. 



Remarks. — Like the other two new species tentatively referred to 

 "LEctypodus, below, this differs from all species referred to Ptilodus in 

 the large length: width ratio and large cusp number of Mi, characters 

 that appear to be surely significant and make closer comparison with 

 species of Ptilodus unnecessary. This, and the next two species, are 

 excluded from Parectypodus by the presence of P3. 



The present form compares very closely with Ecfypodus musculus in 

 all its visible characters. In spite of the small size of the samples, the 

 considerably greater size of ?E. grangeri is almost certainly significant, 

 and its association with wide geographic separation and with a dis- 

 tinct difference in age shows the species to be distinct. 



The principal measurements are given in table 19. 



7ECTYPODUS RUSSELLI Simpson 



Figure 10, b 

 lEctypodus russelli Simpson 1935d, p. 226. 



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

 by A. C. Silberling. 



