Douglass : Vertebrate Fossils from Fort Union Beds. 21 



developed into a rudimentary cusp. From Silberling quarry east of 

 Bear Butte, Montana. 



The mandible (No. 1677) is quite heavy in proportion to the size 

 of the teeth. P^ is high, conical, and sharp-pointed. There is a 

 rudiment of a heel. My is oblong and the posterior is broader than 

 the anterior portion. The two principal antero-lateral cusps are about 

 equal in size, while the antero-median one is much smaller. The pos- 

 tero-lateral cusps are different in size and form. The external one is 

 conical and bordered externally and posteriorly by a cingulum, while 

 the internal cusp is continuous with the cingulum and is inwardly flat- 

 tened. There is a rudiment of a cusp on the cingulum a little inward 

 from the middle of the posterior border of the tooth. From Silber- 

 ling quarry, east of Bear Butte, Montana. 



mm. 



Length of premolar 4-2 



Height of premolar 5-5 



Length of molar 5-5 



Width of molar 4-5 



Height of molar 4-5 



Deltatherium ? Cope. 



(Am. Nat., XV, i88i, p. 337.) 

 (Plate II, figures 1-2.) 



(No. 1698, Carnegie Museum Catalogue of Vertebrate Fossils.) 

 This specimen consists of two upper premolars in a fragment of a jaw. 

 The cusps of the teeth are quite high and sharp-pointed. A section of 

 the anterior tooth is nearly an isosceles triangle, the base being ex- 

 ternal. The cusp is surrounded by a cingulum which, on the inner 

 angle, forms a minute tubercle. The posterior tooth has a transversely- 

 narrower principal cusp, which is somewhat higher, and the inner cusp 

 is comparatively large. There is a small rudimentary conule behind 

 the latter. The tooth was surrounded by a cingulum. Each large 

 external cusp has a small anterior rudimentary accessory cusp. 



mm. 



Length of the two premolars 9-4 



Length of the anterior premolar 5-2 



Length of the posterior premolar 42 



Width of the anterior premolar 4.9 



Width of the posterior premolar 7.3 



