257 



NOTES AND COMMENTS. 



PTYCHODUS TEETH IN CHALK. 



The ' Sharks' palate teeth,' with their hard-ribbed, enamelled 

 surfaces, have long been known to collectors of chalk fossils in 

 Yorkshire and Lincolnshire. Few of these, how^ever, are aware 

 of the probable arrangement of the teeth in the mouth of the 

 fish. Until recently no traces of the cartilaginous jaws have 



Restoration of Mandible of Ptychodus decurrens (Woodward). 



been found in association with the dentition, but by the 

 researches of Mr. H. Willett specimens have been discovered 

 which throw new light on the subject. These are from the 

 Lower Chalk (Holaster suhglohosus zone) at Glynde, Sussex, and 

 are described and figured by Dr. A. Smith Woodward in the 

 May 'Quarterly Journal of the Geological Society.' By the 

 permission of the council of the society we are able to reproduce 



1904 September I. R 



