Divisions of Life and Time 



as those written by the various authors. And 

 just as the events pertaining to the liistory of 

 one small portion of a country might require 

 many volumes for theii' proper record, while a 

 single book might contain all that was to be 

 said of another and much larger section, so one 

 family of animals, or an order even, may com- 

 prise many genera and species, while another 

 may contain but a single species. And one of 

 the first things to be remembered is, that the 

 rank or importance of any division does not de- 

 pend on the number of species it contains, but 

 on the extent to which these agree with or 

 diifer from the members of other groups. 



Eight here it may be well to forestall the 

 complaint that is so often made, that animals 

 are overburdened with long scientific names, 

 and reply to the frequently asked question. 

 Why is it that they have no popular names ? 

 The reply is simple ; a common name can be 

 used only where an object is common, and 

 many living and most fossil animals are so little 

 known as to have received no popular appella- 

 tions. The scientific names given them appear 



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