224 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
unsymmetrically worn specimen, presumably referable to one of the 
antero-lateral series of the upper jaw. The opposite face of the same 
specimen is shown in PI. 3, Fig. 24. 
Fig. 22. Ctenacanthus amblyriphias 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 Pl. 2, Fig. 11. 
Fig. 27. Petalodus alleghaniensis Leidy. Posterior (inner) face of same specimen 
as shown in PI. 2, Fig. 17. 
Fig. 28. Homacanthus 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 Pl. 5, 
Fig. 59. 
Fig. 29. Stethacanthus erectus, sp. nov. Kinderhook limestone; Le Grand, Iowa. 
Left lateral aspect of fragmentary spine. 
Fig. 80. Sagenodus cristatus, sp. nov. Coal Measures; Mazon Creek, Grundy 
County, Illinois. Oral surface of dental plate. 
Fig. 31. Elenichthys 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 Fig. 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 3. 
Figs. 35, 86. Orodus intermedius, sp. nov. Missourian; Weston, Platte County, 
Missouri. Anterior aspect and coronal surface of tooth, X 3. 
