Vol. 67.] AND THEIR DISTRIBUTION IN THE ENGLISH CHALK. 



273 



this tooth has been preserved (PI. XXII, fig. 8). I have not been 

 fortunate enough to discover any examples. 



The range of the English species of Ptychodus is summarized in 

 the following synopsis : — 



















. 













eg 







•S2 





"i 













S 



00 



2 



5^ 



^5 



s 





■S 













►e 



a 





« 





"fe 



• 











"^5 



A 



S 



&J 



a 



<a 



S 





Names of Species 



rg 





69 



S3 



s 



5 







•§ 





3 



8 





and 

 Varieties. 







«0 







&5 



1« 













f>i 





N 





 ^ 



« 



s 



S 



N 



M 











64-1 



e»H 



"4-1 



«*-i 











55 



£t 







O 



O 



O 



O 







O 







Ck 



13 





m 



a> 



0> 



<D 











p« 





■ 











a 









P 



O 



N 



N 



O 



N 



O 







O 

 CS3 





Ph/cJiodus decurrens 



„ vax.multistriatus... 









































„ vav. oweni 























„ var. depressus 

























Pt. latissimus 















1 







Pt. di.coni 



Pt. mammiUaris 









1 













Pt. mortoni 





















? 























1 



Concluding Remarks. 



In concluding these observations on the genus Piycltodvs, it is my 

 pleasant duty to offer my sincere thanks to many friends for their 

 assistance during the compilation of the foregoing facts. Among 

 these I may mention Mr. H. A. Allen, Dr. H. P. Blackmore, 

 Mr. C. Gosling, Mr. W. Murfcon Holmes, Dr. F. L. Kitchin, 

 Mr. E. T. Newton, Mr. It. B. Newton, Dr. A. W. Rowe, Mr. C. 

 Davies Sherborn, Dr. Ivor Thomas, Mr. Toms (of Brighton), 

 Mr. Henry Woods, Mr. George Payne (of Rochester), and Mr. R. M. 

 Brydone. I am also greatly indebted to Mr. Eustace Large for 

 many photographs and lantern-slides during the earlier period of 

 the preparation of this paper, and recently to Mr. Philip Doll man, 

 to whom I am especially indebted for his unceasing interest in 

 connexion with the majority of the lantern-slides, photographs, 



