EXPLANATION OF PLATE XXII. 



Fig. 1-4. Mastodon obscurus: 



Fragments of a lower jaw, from near Santa F6, New Mexico, presented to the Smithsonian 

 Institution by W. F. M. Arny. 



Fig. 1. Portion of the jaw containing the greater part of the last molar tooth. Fig. 2. Por- 

 tion of the symphysis. The two fragments placed in their relative position, and reduced 

 to one-sixth the natural size. 



Fij;. 3. Inferior view of the symphysial fragment, exhibiting exposed portions of the incis- 

 ors. One-fourth the natural size. 



Fig 4. The last inferior molar, uatur.il size, seen on the triturating surface. The back i)or- 

 tion, consisting of another division and the heel, are broken away. 



Figs. 5, 6. Mastodon AMEin.CANUS. Au anomalous molar tooth, natural size. 

 Fig. 5. View of the triturating surface. 

 Fig. G. Side view. 



Fig. 7. GitAPHiODON viNKAitius. A tooth of the natural size. Specimen from the Miocene of Slartha's 

 Vineyard, belonging to the museum of the Smithsonian Institution. 



