Stewart.] Cretaceous Fishes. 395 



PLATE XXVII. 



Fig. 1.— Ptychodus mortoni, end of superior dentition, continuous with left 

 end of fig. 1, plate XXVI, but less reduced. 



Fig. 2. — Ptychodus morion/, a transverse series of teeth, arranged more loosely, 

 from near the right extremity of fig. 1, plate XXVI, about two-thirds natural- 

 size; the upper series belong one at each end of the lower series. 



PLATE XXVIII. 



Ptychodus martini Willist., three-fourths natural size; the teeth were discov- 

 ered disassociated. 



PLATE XXIX. 



Figs. 1, 2, 3. — Ptychodus, sp. indet. 

 Fig. 4. — Ptychodus occidentalis Leidy, natural size. 

 Figs. 5-8.— Ptychodus anonymus Willist., natural size. 

 Fig. 9.— Ptychodus poly gyrus Buckl., a little enlarged. 

 Figs. 10-15. — Ptychodus whipplei Marcou, nearly natural size. 

 Figs. 16-18, 20-22, 24. — Ptychodus anonymus Willist., nearly natural size- 

 Figs. 19, 23, 25, 26, 27. —Ptychodus, spp. 



PLATE XXX. 



Figs. 1-3. — Undetermined lamnids from Kiowa shales, Lower Cretaceous, en- 

 larged one-half. 



Fig. 4. — f Mcsodon abrasus Cragin, enlarged one-half. 



Figs. 5, 6. — Lamna, sp., from Kiowa shales, enlarged one-half. 



Figs. 7, 8. — Corax curvatus Willist., from without and within, enlarged nearly 

 two diameters. 



Figs. 9-11. — ? Ptychodus janewayii Cope, enlarged. 



Fig. 12. — Lamna, sp., enlarged nearly two diameters. Kiowa shales. 



Fig. 14. — Ptychodus poly gyrus, from the side, natural size (the same tooth 

 figured on plate XXIX, fig. 9). 



Fig. 13. — Ptychodus occidentalis, enlarged nearly two diameters. 



PLATE XXXI. 



Figs. 1-40. — Corax falcatus Agassiz, about nine-tenths natural size; isolated 



teeth from many individuals. 

 Figs. 41-46, 50-52. — Isurus mantclli Agassiz, nearly natural size. 

 Figs. 47-49. — Lamna appendiculata Roemer, nearly natural size. 

 Fig. 53. — Ptychodus, sp., enlarged one-fourth. 



