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PAGE. 



Fig. 1, 2. Thrixacodus Nanus, St. J. and W 289 



1 a. Front view of tooth ; 1 &, same enlarged ; 1 c, base from below. Kinderhook beds, 



Barlington, Iowa. 



2 a. Side view of another specimen, showing the base ; 2 6, the same enlarged. Same 



horizon and locality. 



Lambdodus COSTatus, St. J. and W 280 



Front view of tooth ; 3 b, side view ; 3 c, outline from above. Upper Barlington 

 limestone, Louisa county, Iowa. 



Lambdodu s tbansyersus. St. J. and W 282 



Front view of tooth enlarged two diameters ; 4 &, side view. St. Louis lime- 

 stone, Alton, 111. 



Lambdodus calceolus, St. J. and W ...281 



Front view; 5 6, vie w from above ; 5 c, side view. Upper Burlington; Louisa 

 county, Iowa. 



Lambdodus robustus, St. J. and TV 282 



Views from the front, above and side. Keokuk limestone. 



Htbocladodus nttidus, St. J. and TV 288 



Front view of tooth, enlarged four diameters ; lb, posterior face j 7 c, front view, 

 showing inferior basal region ; 7 d, base from below ; 7 e, profile section. 

 Cheater limestone; Chester, 111. 



Htbocladodus compressus, (N. and TV. ap.) 287 



Views of outer and posterior faces, and profile section. Upper Burlington ; 

 Louisa county, Iowa. 



Hybocladodus plicatilis, St. J. and TV 286 



Views of outer and posterior faces, and profile section. Upper Burlington ; 

 Louisa county, Iowa. 



Htbocladodus texuicostatus, St. <X. and TV 286 



Outer and inner faces, and profile section. Keokuk limestone ; Illinois. 



Htbocladodus, var. inteiemedius, St. J. and TV 287 



View of outer face, and profile section. Keokuk limestone. 



Mesodmodus osnatub, St. J. and TV 294 



View of outer face of tooth, enlarged two diameters; 12 &, the same further 



enlarged; 12 c. posterior face; 12 d, base from below ; 12 e, profile section, 



enlarged same as 12 b. Upper Burlington ; Louisa county, Iowa. 

 Similar views of a less robust specimen. Same horizon and locality. 

 Similar views of a strong, worn tooth. Same horizon and locality. 



Mksodmodus explanatus, St. J. and W 293 



View of posterior face of symmetrical tooth ; 15 6, outer face, enlarged two 



diameters; 15 c, base from below; 15 d, profile section. Kinderhook beds, 



Burlington, Iowa. 

 Outer face of eccentric tooth, enlarged two diameters ; 16 &, view of base from 



below ; 16 c, profile section. Same horizon and locality. 

 Posterior face, and profile section of an abnormal or eccentrically developed 



tooth, enlarged one-half. Same horizon and locality. 



Fig. 



3. 

 3 a. 





Fig. 



4. 



4 a. 





Fig. 



5. 

 5 a. 





Fig. 



6. 



6 a, b, c. 





Fig. 



7. 

 7o. 





Fig. 



8. 



8 a, b, c. 





Fig. 



S. 



9 a, 6, c. 





Fig. 



10. 



10 a, b, ft 





Fig. 



11. 



11 a,l. 





Fig. 



12-14. 



12 a. 







13 a, b. c. 



14 a, b,c, 



d. 



d. 



Fig. 



15-17. 

 15 a. 





