38 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 42. 



of the position of the upper shaft with relation to the symphysis of 

 the upper jaws and to the snout of the animal is more difficult, but 

 the present writer has now little doubt that nature had the problem 

 solved in a way that permitted the presence of a spiral of teeth above 

 and another below. 



EXPLANATION OF THE PLATES. 

 [All the figures are three-fourths the natural size.] 



Plate 1. 



1. Upper tooth shaft. 



2. Lower tooth shaft. 



3. Detached portion of lower shaft. 



4. Seventh tooth of lower shaft. 



5-7. Fifth, sixth, and seventh teeth of the upper shaft. 



9. Depression occupied by left side of lower jaw. 



11, 12. Smaller teeth supposed to have belonged to some of the jaws. 



13. Fragment of cartilage supposed to belong to the right half of lower jaw. 



14. Placed just above the nasal pit. 



15. Process of cartilage, possibly the antorbital process. 



16. 17. Position of two broken teeth belonging to the upper shaft. 



Plate 2. 



figure 1. 

 2. Fragment of lower tooth shaft. 

 5-7. Impressions of teeth of upper shaft, indicated as on Plate 1. 



8. Part of right side of lower jaw. 



9. Part of the left side of the lower jaw. 



10. Impression in the shale of part of the right side of the lower jaw. 



figure 2. 



4. The tooth indicated by the same numeral in Plate 1. 

 12. The tooth indicated in Plate 1 by 12. 



18. The sixth tooth of the lower shaft. 



19. A loose shaft tooth. 



20. A tooth supposed to belong to one of the jaws. 



