PLATE V I . 



Page. 



CHITONODUS LIKATUS, St. J. and W 110 



Fig. la. Maxillary posterior tooth, right ramus, view from above of an imperfect ex- 

 ample, posterior extremity restored in outline; 1 b, do., from the inner 

 margin. St. Louis limestone; Alton, 111. 



CHITONODUS ANTIQUUS, St. J. and W 116 



Fig. 2 a. Mandibular posterior tooth, left ramus, view from above, outline partially 

 restored; 2 b, do., transverse profile from inner margin; 2 c, do., outer 

 inrolled margin; 2d, do., from the antero-lateral border. Lower Bur- 

 lington, Iowa. Prof. Worthen. 



CHITONODUS SPKINGERI, St. J. and W 112 



Fig. 3 a. Maxillary posterior tooth, left ramus, view from above of a worn example, 

 outline partially restored; 3 b, do., from inner margin; 3 c, do., outer in- 

 rolled margin; 3 d, do., from the anterior border, foreshortened. Upper 

 Burlington; Augusta, Iowa. Mr. Wachsmuth. 



Fig. 4n. Same form, right ramus, a worn specimen, seen from above; 4 b, do., inner 

 margin; 4 c, do., outer inrolled margin; 4 (J, do., from anterior border, 

 foreshortened. Upper Burlington; Louisa county, Iowa. Mr. Springer. 



Fig. 5 a. Mandibular posterior tooth, left ramus, view from above; 5 b, do., inner 

 margin; 5 c, do., from antero-lateral border; a worn example, showing 

 merely a trace of transverse imbrications. Upper Burlington; Augusta, 

 Iowa. O. St. John. 



Fig. ti a. A worn, medium-size example of the saino form, seen from above; 6 b, do., 

 inner margin; 6 c, do., outer inrolled margin; 6 d, do., from the anterior 

 border. Upper Burlington; Augusta, Iowa. Mr. Springer. 



Fig. 7 a. Mandibular median tooth, left ramus, a worn specimen, seen from above, 

 outer extremity restored in outline; 7 b, do., inner margin, transverse 

 profile; 7 c, do., outer margin; 7 d, do., from antero-lateral border; 7 e, 

 do., postero-lateral border. Upper Burlington; Louisa county, Iowa. 

 Mr. Springer. 



Fig. 8 a, b, c, d, e. Similar views of a more prominently rigid, woru example of the 

 same form, outline partially restored. Upper Burlington; Augusta, 

 Iowa. 



Fig. a. Maxillary posterior tooth, left ramus, a medium-size example, preserving 

 the transverse imbrications over a portion of the anterior neck, seen 

 from above, outline partially restored; 96, do,, inner margin, trans- 

 verse profile; 9 c, do., from anterior border; 9 d, from posterior ex- 

 tremity. Upper Burlington; Louisa county, Iowa. O. St. John. 



Fig. 10 a. A large, robust example of the same form, from above, partially restored 

 in outline; 10 b, do., inner margin; 10 c, do., outer inrolled margin; W d, 

 do., from anterior border, foreshortened. Upper Burlington; Augusta, 

 Iowa. 



'Fig. II a. A similar example of the same form, seen from above, outline restored. 

 Upper Burlington; Pleasant Grove, Iowa. Prof. Worthen. 



Fig. 12 a . Mandibular posterior tooth, right ramus. showing transverse imbrications, 

 view from above, outline restored. Upper Burlington; Louisa county, 

 Iowa. O. St. John. 



