Norwich Geological Society. 579 



analyzed, and the phosphatic nature and consequent agricultural 

 value of these stones might possibly for centuries to come have 

 remained unknown. 



He had no theory of his own to advance in explanation of the 

 formation of Crag coprolite stones, thougli it appeared to him that 

 they had some points in common with the occurrence of flint stones 

 in Chalk, In the Chalk wo see flint setting, so to speak, upon the 

 root of a sponge or ventriculite, and forming around it an oval or 

 spherical mass, while the rest of the ventriculite, when circumstances 

 often admit of the observation being made, can be traced in the con- 

 tiguous mass of Chalk. But as the workmen in chalk quarries break 

 up the chalk in small pieces, a ventriculite in connexion with its 

 flint-invested root is rarely presented to our notice, Now tlierewere 

 no rooted ventriculites in the Crag Sea for the Crag phosphatic or 

 so-called coprolitic matter to adhere to ; but there were an abundance 

 of sharks' teeth with roots, and upon these roots or fangs we find 

 the phosphatic stone clinging in a more or less spherical mass, 

 while the greater portion of the organic body — that is, the tooth 

 proper, has none of this phosphatic investment. And when the 

 Crag is broken up, were these teeth delicate and fragile, they would, 

 after the fashion of the Chalk ventriculites, break away from their 

 stone-invested roots. 



Chalk flint-stones when broken often present to us enclosed shells, 

 sharks' teeth, and. other organic bodies. But in all cases these flint- 

 enclosed organic bodies are of the same species as the organic bodies 

 found in the Chalk itself. It is otherwise with the organic bodies 

 enclosed in the Crag phosphatic stones. We find these stones l3^ing 

 in immediate contact with numerous shells, but if we break a phos- 

 phatic stone, and find a shell enclosed, this Crag stone-enclosed shell 

 is not of the kind found in the Crag, but of some species found in 

 the underlying and much more ancient formation than Crag, the 

 London Clay. And though the shark's teeth which are enclosed in 

 these Crag stones may be quoted as an exception to this rule, yet 

 they really support it, for there are two groups of shark's teeth 

 found in the Crag, one group containing species peculiar to the Crag, 

 the other containing species which are found in both the Crag and 

 the London Clay. Now, whenever a Crag shark's tooth is in a phos- 

 phatic nodule, or even if it have the smallest piece of phosphatic 

 matter investing it, it is invariably a tooth of the London Clay 

 group. Again, no phosphatic stone has ever been seen investing one 

 of the many thousand teeth of the whale tribe which have turned 

 up at the diggings, and it is a well-known fact that these Cetacean 

 teeth are not found in the London Clay, but are a specialty of the 

 Crag ; so that we may set it down as a rule, so far as the Crag is 

 concerned, that we only find Crag fossils in union with phosphatic 

 stone when the fossil is of a London Clay species : and this leads to 

 the inevitable conclusion that all the Crag coprolite stones were 

 originally in the London Clay. The soft London Clay itself, when 

 it formed the bed of the Crag ocean, would be abraded by the action 

 of tides and currents, bringing about the separation from it of the 



