BASIN OF LONDON. 359 



Judging from the character of the crag fauna, it has been 

 conjectured that these deposits were formed in a sea of 

 moderate depth, from fifteen to twenty-five fathoms. Many 

 of the species formerly known only as fossils of the crag, and 

 supposed to have died out, have been dredged up in a living 



FIG. 258. Carcharias megalodon, Red crag. 



