6 ELEPHANTS. 



found in the earlier forms. Finally, we have materials for 

 discussing the probable relationship of the elephants to some 

 other groups of animals. 



Fortunately for the present purpose the British Museum 

 possesses the most extensive series of Proboscidean remains 

 to be found anywhere, so that except in very few instances 

 readers can see in the S.E. Gallery of Geology the actual 

 specimens, or, at any rate, casts of the specimens, upon which 

 the following descriptions are based, and can to some extent 

 check the accuracy of the various statements for themselves. 



Before proceeding to the description of the animals, it may 

 be advisable to refer to the geological horizons or periods of 

 the Earth's history during which they existed and in the rocks 

 of which their fossil remains are found ; for it is necessary to 

 know the order in which the different forms appeared on the 

 earth, just as in tracing the pedigree of a human family, 

 the dates of the documents upon which it is founded must 

 be known. It will be seen from the following table that the 

 history of the life of the Earth falls into several great periods 



TABLE 1. 



f QUATERNABY .............. f RECENT. 



Ji PLEISTOCENE. 



- 



TEBT.ABY ... ...... ;^v... MIOCENE. 



j OLIGOCENE, 

 I EOCENE. *~ 

 f CRETACEOUS. 

 MESOZOIC or SECONDARY .............. J JURASSIC. 



[ TBIASSIC. 

 f PERMIAN. 



CARBONIFEROUS. 

 PALAEOZOIC or PRIMARY .......... ...... j DEVONIAN. 



j SlLUBIAN. 



I ORDOVICIAN. 

 ^ CAMBRIAN. 



to which names have been given by geologists. The earliest of 

 these is called the Primary or Palaeozoic Period, and during 



