Geology 



and the Ordovices ; and Cambrian from Cambria or 

 Wales. 



Carboniferous means carbon-bearing, and has re- 

 ference to the fact that most of the coals worked in 

 the British Isles are in that formation. 



Of the names of smaller subdivisions some are place- 

 names, some have reference to the nature of the rocks 

 and the uses to which they have been put, e.g. Millstone 

 Grit, while yet others are local names in use by 

 farmers and quarrymen and adopted by the earlier 

 geologists. 



The fossils which are found in the stratified rocks 

 have been preserved in various ways. In some cases 

 the actual matter of the hard parts of animals, such as 

 shells and bones, has been preserved ; in others this has 

 been replaced by another mineral substance, such as 

 silica or carbonate of iron. Sometimes mere casts or 

 impressions bear testimony to the former presence of 

 organisms. 



It is not intended to enter into the question of the 

 classification of the animal kingdom, in the present work, 

 but it may be well to briefly explain the system of naming 

 animals and plants. 



Of course there are, even amongst creatures at 

 present living, far too many different beasts for us to 

 give them all common names, such as cow, cod, or gnat, 

 and indeed many of the names in general use are applied 

 to a large number of different creatures, and are therefore 

 not sufficiently accurate for scientific purposes. 



It is found on studying animals, and the same is true 

 of plants, that they fall into groups having many features 

 in common, while nevertheless possessing characters of 



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