224 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



unsynimetrioally worn specimen, presumably referable to one of the 



anterolateral series of the upper jaw. The opposite face of the same 



specimen is shown in PI. 3, Fig. 24. 

 Fig. 22. Ctenacanthus ambli/xiphias Cope. Atchison shales (Missourian) ; South 



Bend, Cass County, Nebraska. Left lateral aspect of fragmentary 



spine referable to the first dorsal fin. 

 Fig. 23. Ctenacanthus amblyxiphias Cope. Atchison shales (Missourian) ; Louisville, 



Cass County, Nebraska. Left lateral aspect of fragmentary spine 



showing characteristic ornamentation. 



The original of Fig. 12 is preserved in the Museum of Comparative Zoology 

 at Cambridge, the remainder in the Museum of Nebraska State University at 

 Lincoln. 



PLATE 3. 



[All figures are of the natural size.] 



Fig. 24. Janassa maxima, sp. nov. Anterior (outer) coronal aspect of same speci- 

 men as shown in PI. 2, Fig. 21. 



Fig. 25. Peripristis semicircularis (N. and W.) Summit of Chester limestone; 

 Montgomery Switch, Caldwell County, Ky. Lateral aspect of upper 

 tooth, the root partially imbedded in matrix. 



Fig. 26. Fissodus inaequalis (St. J. and Worth.) Lateral aspect of same specimen 

 as shown in PI. 2, Fig. 11. 



Fig. 27. Petalodus alleghaniensis Leidy. Posterior (inner) face of same specimen 

 as shown in PI. 2, Fig. 17. 



Fig. 28. Ilomacanthus delicatulus, sp. nov. Kinderhook limestone ; Le Grand, 

 Iowa. Spine referred to the first dorsal fin of a very small indivi- 

 dual. An enlarged view of the same specimen is shown in PI. 5, 

 Fig. 59. 



Fig. 29. Stethacanthus erectus, sp. nov. Kinderhook limestone ; Le Grand, Iowa. 

 Left lateral aspect of fragmentary spine. 



Fig. 30. Sacjenodus cristatus, sp. nov. Coal Measures; Mazon Creek, Grundy 

 County, Illinois. Oral surface of dental plate. 



Fig. 31. Elonichthys disjunctus, sp. nov. Coal Measures ; Mazon Creek, Grundy 

 County, Illinois. Complete but somewhat distorted individual. 



The originals of Figs. 25 and 28 are preserved in the Museum of Comparative 

 Zoology at Cambridge ; those of Figs. 24, 26, and 27, in the Museum of Nebraska 

 State University; of P'ig. 29 in the United States National Museum; and of Figs. 

 30 and 31 in the Museum of Yale University. 



PLATE 4. 



Figs. 32-34. Chomatodus inconstans Newb. and Worth. Keokuk limestone ; Keokuk, 

 Iowa. Coronal surface, anterior face, and transverse section of 

 tooth, X f. 



Figs. 35, 36. Orodus intermedius, sp. nov. Missourian ; Weston, Platte County, 

 Missouri. Anterior aspect and coronal surface of tooth, X |. 



