EXPLANATION OF PLATE XVIII. 



All the figures are of the natural size except Figs. 51, 5'2. 



Figs. 1-14. Ptychodus MoitxoNl: 



Figs. 1, 2. Upper and posterior views of a large tootli from Kansas, obtained by Dr. George 



M. Sternberg. 

 Figs. 3, 4. Upper and posterior views of auotber tootb, apparently from the same individual. 

 Figs. 5, C. Upper and posterior views of another tooth from the same locality. 

 Figs. 7, 8. Upper and posterior views of another tooth from the same locality. 

 Figs. 9, 10. Upper and posterior views of another tooth from the same locality. 

 Figs. 11, 12. Upper and anterior views of a large tooth from near Columbus, Mississippi, 



found by Dr. William Sinllman. 

 Figs. 13, 14. Upper and posterior views of a tooth from Green County, Alabama, obtained 



by Professor Joseph Jones. 



Figs. 1.5-18. PTYCHonus occiDHNTA'Lis. Specimen obtained near Fort Hays, Kansas, by Dr. John L. 

 Le Conte. 

 Figs. 15, 16. Upper and posterior views of a worn tooth. 

 Figs. 17, 18. Upper views of two small teeth. 



Figs. 19, 20. Ptychodus Whippleyi. The specimen obtained in the Cretaceous formation of Texas, by 

 Dr. Benjamin F. Shiimard. 

 Fig. 19. Upper view of a tooth. 

 Fig. 20. Posterior view of the same tooth. 



Figs. 21-25. OXYRHINA EXTE.VTA : 



Figs. 21-23. Views, external or anterior, of three teeth from the Cretaceous formation of 



Kansas, obtained by Dr. George M. Sternberg. 

 Figs. 24, 25. External v.iews of two teeth, from the Cretaceous formation near Columbus, 



Mississippi, obtained by Dr. William Spillman. 



Figs. 26-28. Otodus divaricatus. The specimen from Texas, probably from a Cretaceous formation. 

 Loaned for examination by Dr. William Spillman. 

 Fig. 2fi. External or anterior view of the tooth. 

 Fig. 27. Lateral view reversed. 

 Fig. 28. Internal or posterior view. 



Figs. 29-40. Galeocerdo falcatus. External views of teeth. 



Figs. 29-31. Specimens from the Cretaceous of Kansas, collected by Dr. George M. Sternberg. 

 Figs. 32-36. Specimens from the Cretaceous, near Columbus, Mississippi, collected by Dr. 



William Spillman. 

 Figs. 37-40. Specimens from the Cretaceous, near Fort Hays, Kansas, collected by Dr. John 



L. Lo Conte. 

 Figs. 41, 42. Specimens from the Cretaceous of Texas, collected by Dr. Benjamin F. Shumard. 

 Fig. 43. Specimen from the chalk of Sussex, England. 



Figs. 44, 45. Lamna : 



Fig. 44. External view of a tooth, from the Cretaceons, near Fort Hays, Kansas, found by Dr. 



John L. Le Conte. 

 Fig. 45. External view of a similar but smaller tooth, from the chalk of Sussex, England. 



Figs. 4G-49. Lamna : 



Figs. 46, 47. Specimens from the Cretaceous of New Jersey. Fig. 46. Lateral view of a tooth. 

 Fig. 47. E::terual view of another specimen. 



Figs. 48, 49. Specimens from the Cretaceous of Missisnppi, collected by Dr. William .Spill- 

 man. Fig. id. Lateral view of a tooth. Fig. 4). External view of another tootli. 



Fig. .50. Outer view of a tooth. Specimen from the Cretaceous of Kansas, collected by Pro- 

 fessor Hayden. 



Figs. 51, 52. Pal/EOSY<ops paludosos. Oue-half the natural si7,e. - 



Fig. 51. Side view of the face; from the same specimen as the teeth of Fig. 3, Plate IV. 

 Fig. 52. Lower jaw; repeated from the same specimen as Fig. 11, Plate V. 



