EXPLANATION OF PLATE 19. 



Figures 1-7 are reproduced one and one-half times natural size; figures 8-11 

 are reproduced natural size. 



Figs. 1-3. Thomomys microdon n. sp. Superior, inferior and lateral views 

 of the type specimen. 



Figs. 4-6. Teonoma spelaea, n. sp. Superior, lateral, and inferior views 

 of the type specimen. 



Fig. 7. Teonoma spelaea. Superior view of the mandible. 



Figs. 8, 9. Aplodontia major fossilis, n. sub-sp. External and internal 

 views of the right ramus of the mandible. 



