34 CRETACEOUS GROUP &C. 



other words, that they were contemporaneous beings. 

 Whatever cause laid bare the eastern portion of the se- 

 ries, appears to have acted simultaneously on the western 

 mass : not a rush of currents, but either a subsidence of 

 the sea, or elevation of the land, which has left the fossils 

 in their original beds unbroken, and, as to their external 

 form, unaltered. 



In conclusion, I beg leave to state, that this work has 

 been written during the constant interruptions of a pro- 

 fessional life ; and I cast it as a grain of sand on the moun- 

 tain of geological knowledge, which has been heaped up 

 by the genius and industry of the naturalists of both he- 

 mispheres. 



