PLATE XLVIII. 



Fig. Page. 



1-5. PtychoditH rugosus, Dixon; associated teeth, crown-view, one (1) of 

 upper middle row, twice nat. size, the others of paired rows, nat, 

 size. — Zone of Micraster corangtdnum ; Purley, Surrey. B. M. no. 

 39793. 232. 



6. Ditto; tooth, crown-view, outline-section (0(/), and side view (6&), nat. 



size. — Senonian zone ; Sussex. Man tell Collection (B. M. no. 4428). 232. 



7. Ditto; tooth, crown-view, outline-section (7 a), and side view (7 b), nat. 



size.— Ibid. Dixon Collection (B. M. no. 28247). 232. 



8-11. Ditto : associated teeth, crown- view, and two (8 a, 9 a) also in outline- 

 section of crown, nat. size. — Senonian zone ; Kent. Taylor Collec- 

 tion (B. M. nos. 33249, 32352). 232. 



12. Ptychodus polygyrus var. marginalis, Agassiz ; one of the type teeth, 



crown-view and (12a) outline-section of crown. — Turonian zone; 

 Lewes. Mantell Collection (B. M. no. 4385). 234. 



13, 14. Ditto ; associated set of teeth of various upper and lower rows indi- 



cated by lettering, nat. size. — Zone of Terebratulina gracilis ; Would- 

 ham, Kent, G. E. Dibley Collection (B. M. no. P. 104G4). 234. 



15, 16. Ditto ; associated teeth of lower middle (15) and upper inner paired 

 rows (16), both in crown-view, the first also in side view to show 

 two pressure scars (15^), nat. size. — Chalk; Beachy Head, Sussex. 

 B. M. no. P. (3141. 235. 



