Douglass : Vertebrate Fossils from Fort Union Beds. 25 



No. 1686 (Plate I, Fig. 14) is much larger antero-posteriorly than 

 No. 1690, has a much larger heel and a larger anterior cusp. 



No. 1678 (Plate II, Fig. 11) is a portion of a mandible with two 

 premolars in position. The teeth are moderately high and are not 

 large in proportion to the size of the mandible. The teeth are slightly 

 spaced. Both are simple, compressed-conical cusps with minute 

 heels. The second premolar is longer antero-posteriorly than the 

 first one which is represented in the specimen. 



EXPLANATION OF PLATES. 



Plate L 



Fort Union Mainviah. 



Figs. 1-2. A lower molar tooth. Carnegie Museum Catalogue of Vertebrate Fos- 

 sils, No. 1691. Fig. I, lateral view. Fig. 2, top view. X4-5- 



Fig. 3. Tooth with serrated posterior border. Silberling Collection. X 4-5- 



Fig. 4. Etiprotogottia. No. 1016. A premolar. Top view. X 2.25. 



Figs. 5-6. Megoptenia 7}iinuta. No. 1675. Type of genus and species. Fig. 5, 

 top view of teeth. Fig. 6, side view of portion of mandible with teeth. ^ 9. 



Figs. 7-8. Lower molar tooth. No. 1692. Side and posterioroblique views. X4-5 



Figs. 9-10. Picrodits silbeilingi. No. 1 670. Type of genus and species. Top 

 and external views of mandible with two teeth. X 9- 



Fig. II. Premolar tooth No. 1689. X 2.25. 



Fig. 12. Premolar tooth No. 1690. X2.25. 



Fig. 13. Premolar tooth No. 1687. X4-S- 



Fig. 14. Premolar tooth No. 1686. X 4-5- 



Fig. 15. Protochriacus ? No. 1928. X 2.25. 



Fig. 16. Ptilodus. No. 1933. Top view. X4-5- 



Fig. 17. Cimolestes ? No. 1013. Left ramus of mandible. X^-S 



Fig. 18. Incisor tooth. Silberling Collection. Side view. The other side rep- 

 resented in Fig. 19. X4-5- 



Fig. 19. Ptilodus Montanus. No. 1673. Type. Portion of mandible with two 

 teeth. X4-5- 



P'ig. 20. Same specimen as Fig. 18. View of opposite side. X 4-S- 



Plate II. 

 Fort Union Mammals. 



Figs. 1-2. Deltatherium ? Carnegie Museum Catalogue of Vertebrate Fossils, 

 No. 1698. Two upper premolar teeth in portion of maxillary. Fig. i, external 

 view. X ^-TS- Fig. 2, crown view of teeth. X I-75- 



Figs. 3-4. Coriphagus montanus. No. 1669. Type of genus and species. Fig. 

 3, outer view of ramus of mandible. X ^-S- Fig. 4, top view of teeth. X 3- 



Figs. 5-6. Tricentes ? No. 1676 Views of molar tooth. X4-S- 



