6 DEFINITION OF TERMS. chap. I. 



fossil quadrupeds belongs to extinct species. 1 am aware that 

 it may be objected, with some justice, to this nomenclature, 

 that the term Post-pliocene ought in strictness to include all 

 geological monuments posterior in date to the Pliocene; 

 but when I have occasion to speak of these in the aggregate 

 I shall call them Post-tertiary, and reserve the term Post- 

 pliocene exclusively for Lower Post-pliocene, the Upper Post- 

 pliocene formations being called "Eecent." 



Cases will occur where it may be scarcel}' possible to draw 

 the line of demarcation between the Newer Pliocene and Post- 

 pliocene, or between the latter and the recent deposits ; and 

 we must expect these difficulties to increase rather than 

 diminish with every advance in our knowledge, and in propor- 

 tion as gaps are filled up in the series of geological records. 



In 1839 I proposed the term Pleistocene as an abbreviation 

 for Newer Pliocene, and it soon became populai-, because 

 adopted by the late Edward Forbes in his admirable essay 

 on " The Geological Eelations of the existing Fauna and 

 Flora of the British Isles j'"^ but he applied the term almost 

 precisely in the sense in which I shall use Post-pliocene in this 

 volume, and not as short for Newer Pliocene. In order to 

 prevent confusion, I think it best entirely to abstain from 

 the use of Pleistocene in future; I have found that the 

 introduction of such a fourth name (unless restricted solely to 

 the older Post-tertiary formations) must render the use of 

 Pliocene, in its original extended sense, impossible, and it is 

 often almost indispensable to have a single term to compre- 

 hend both divisions of the Pliocene period. 



The annexed tabular view of the whole series of fossiliferous 

 strata will enable the reader to see at a glance the chrono- 

 logical relation of the Eecent and Post-pliocene to the ante- 

 cedent periods. 



* Geological Relations of the Survey of Great Britain, vol. i. p. 336. 

 existing Fauna and Flora of the London, 1846.) 

 British Isles. (Memoirs of Geological 



