PLATE VI Continued. 



A small example of the same form, left ramus, seen from above (repre- 

 sented too obliquely inrolled); 13 l>, do., inner margin, transverse pro- 

 file; 13 c, do., outer inrolled margin; 13 d, do., from anterior border. 

 Upper Burlington; Pleasant Grove, Iowa, 



Fig. 14 a. Mandibular median tooth, left ramus, showing imbrications, seen from 

 above, outline restored; 14 b, do., inner margin, transverse profile; Me, 

 do., outer margin; 14 d, do., from antero-lateral border; 14 e, do., pos- 

 tero-lateral border and longitudinal profile. Upper Burlington; Bur- 

 lington. Iowa. O. St. John. 



Fig, 15 a. A larger, worn example of the same form, from above, outline restored; 

 15 b, c, do., views from the antero and postero-lateral borders. Upper 

 Burlington; Louisa county, Iowa. Mr. Springer. 



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