PLATE XII 



PAGE- 



Fig. 1-4. Petalokhyncrus pseddosaggitatus, St. J", and "W 405 



1 a. Convex face of small tooth ; 1 b, concave face ; 1 c, profile section. St. Louis beds, Pella, 



Iowa. 



2 a. Concave face of large tooth ; 2 b, convex aspect ; 2 e, profile section. St. Louis ; Alton, 



Illinois. 



3 a. Outline of convex face of very large acuminate tooth, with forked root. Same horizon 



and locality. 



4 a. Similar outline of medium-sized, symmetrical tooth. St. Louis; Pella, Iowa. 



Fig. 5,6. Petalokhyxchus spatulatus, St. 0". and W 408 



5 a. Convex aspect of large tooth with tumid apex; 5 6, side view. St. Louis limestone; 



Alton, Illinois, 



6 a. Convex face of small tooth; 6 b, concave face; G c, profile section. St. Louis; Pella, 



Iowa. 



Fig. 7,8. Petalouuyxchus distoutus, St. I. and W 406 



7 a. Convex face of medium-sized tooth ; 7 b, concave faee showing deeply arched basal mar- 



gin; 7 c, profile section. St. Louis beds; Pella, Io,wa. 

 8a,&,c. Similar views of smaller specimen. St. Louis: Alton, Illinois. 



Fig. 9. Ctexopetalus bellulus, St. J. and W 398 



9 a. View of group of teeth from the convex side, enlarged two diameters; 9 b, view of 

 opposite face, showing entire outline of the largest specimen; 9 c, profile section of 

 large tooth. St. Louis beds ; Pella, Iowa. 



Fig. 10. Petalodus hybridus, St. J. and W 394 



10 a. Convex face of large tooth ; 10 b, concave face ; 10 c, profile section. St. Louis ; Alton, 



Illinois. 



Fig. 11. Petalodus peoxxmus, St. J. and "W 395 



11 a. Convex face of nearly perfect tooth ; 11 &, view of concave face ; 11 c, profile section. 



Upper Coal Measures, Springfield, Illinois. 



Fig. 12. Petalodus cuxtTus? N. and TV 394 



12 a. View of convex face of medium-sized tooth; crest worn nearly plane with convex 



basal margin ; 12 b, concave face, showing corrugated ornamentation ; 12 c, pro- 

 file section. Keokuk limestone, Bentonsport, Iowa. 

 Fig. 13. Ctexopetalus ytxosus, St. J. and TV 396 



13 a. Convex crown-face ; 13 6, profile section. Keokuk limestone, Bentonsport, Iowa. 



Fig. 14. Ctexopetalus occtdextalis, St. J. and W- 401 



14 a. View of convex face; 14 &, concave face; 14 c, profile section. Lower Coal Measures, 



Fort Dodge, Iowa. 



Fig. 15. Ctexoptychtus Stevexsoxi, St. J. and TV 383 



15 a. View of convex face; 15 b, concave face; 15 c, profile section. Coal Measures, "West 



Virginia. 



Fig. 16, 17. Calopodus apicalis, St. J. and TV •. . .403 



16 a. Convex face of tooth, enlarged two diameters ; 16 b, concave aspect; 16 c, profile out- 



line. Middle Coal Measures, Iowa. 



17 a. Convex face of smaller tooth, enlarged, two diameters; 17 &, concave face showing 



hooked apex ; 17 c, profile outline. Same horizon and locality. 



Fig. 18. Ctexopetalus lbiatulus, St. J. and TV 399 



18 a. View of convex face ; 18 b, profile section. Chester limestone, Chester, Illinois. 



