76 



CRETACEOUS GROUP. 



four feet in length, and is preserved in the museum at Paris. Other paitd 

 have also been found from time to time in the Maastricht quarries, and som& 

 fragments in the chalk of the south of England." Ansted. 



The whole length of the animal was probably not less than twenty-foui 

 feet, a magnitude which must be compared with that of the lizards of the 

 present day, and not with the crocodilians, whose structure is totally dif- 

 ferent. 



18. We also find in the chalk formation ceta'ceous mammals, 

 which are classed among the lamantins and dolphins. 



19. The CRETA'CEOUS GROUP prevails extensively in England 

 and on the continent of Europe. True white chalk exists not 

 only in England, but also in France, in Denmark, in Poland, in 

 central Russia, and in the Caucasus. Semicrystalline rocks of the 

 oreta'ceous epoch also exist in the central plains of Asia Minor. 

 Beds of the creta'ceous period are found in New Jersey, and other 

 parts of the United States ; but they rest on the oldest secondary 

 rocKs, without the intervention of the o'olite. The formation is 

 extremely calcareous, in places chiefly arenaceous, but no true 

 chalk has yet been discovered in America ; nor has o'olite been 

 found. Fossils, apparently creta'ceous, have been recently obtained 

 from south-eastern India. 



This brings us up to the close of the secondary formation. As 

 far as we have studied our subject, we find the earth's crust to con- 

 sist of a series of formations, as represented in the following dia- 

 gram (fig. 146). 



Secondary. 



Chalk with flints. 

 Chalk without Hints. 

 Chalk marl. 

 Green sands. 

 Wealden. 



Cretaceous System. 



O'olitic System. 



Upper m'\v red sandstone, or Triaseic System^ 



Lower new red sandstone, or Permian System. 

 Carboniferous System. 



Old red sandstone. 



Transition. 



Metamorphic. 

 Plutonic Rocky 



f Devonian System. 

 < Silurian System. 



Cambrian System. 

 Argillaceous Schist. 

 Mica Schist. 

 Gneiss. 

 Granite. 



Fig. 146. 



18. What mammals are found in the chalk formation? 



19. What is the extent of the creta'ceous group ? Has chalk been found 

 in the creta'ceous formation of the United States ? 



