NOMENCLATURE. v 



Pleiocene species may have become extinct, while in the latter, or as he terms them the 

 '" Post-tertiary strata," all the marine forms are still living in the European seas. But that 

 is not a difference of sufficient magnitude to establish so important a division. Most of 

 the living marine Mollusca, if not all, are to be found in the Pleiocene strata, and there- 

 fore there is no break of molluscan life to indicate the close of a great life-period. Nor 

 in the case of the Mammalia living on the land is there any marked break cf continuity 

 from the Meiocene down to the present day ; but all are so interlaced together that the 

 line of demarcation between the Tertiary and living is, to a great extent, arbitrary. The 

 Pleiocene, therefore, cannot be viewed as the closing stage of the Tertiary or Csenozoic 

 period, but the latter term must be extended so as to embrace the lapse of time from the 

 Eocene down to the present day. 



The term Pleistocene (or ttXuotos, most, Kaivd^, new), first used by Sir Charles Lyell 

 in 1839, and subsequently discarded for "Post-pliocene," seems to me to be the most 

 convenient name for the stage which followed the Pleiocene, since so far as the mam- 

 malian life is concerned the numbers of living species preponderated over the extinct in the 

 proportion of at least three to one. The terms " Postpliocene," as well as the " Qua- 

 ternary " of the Erench and the " Quarternary " of some of the American geologists, lie 

 open to the objection urged above, that they convey a false idea of the magnitude of the 

 break between the Pleiocene and the succeeding period. I shall therefore in this treatise 

 confine myself to the use of Pleistocene, a name widely used both in Britain and on the 

 Continent, and a name that is the etymological consequent of Eocene, Meiocene, and Pleio- 

 cene. 1 The consideration of the subdivisions of the Pleistocene, preglacial, glacial, and post- 

 glacial, must be postponed till I can bring forward the evidence by which I have been led 

 to reject them as being of no value in the classification of the mammalia, a view held 

 in common by Prof. Phillips 2 and by Mr. Godwin- Austen. 3 Sir Charles Lyell in like 

 manner ignored the glacial period as a means of subdividing the " Post-pliocene " life- 

 period. 4 The terms are merely valuable as denoting physical changes in Britain, North 

 Germany, Russia, and Scandinavia. 5 



The classification of the Tertiary groups of life from the Eocene to the Pleistocene is 

 based on the recognition of the gradual evolution of animals which bear an increasing 

 resemblance to those which are now alive. At this point, however, this principle of classi- 

 fication is valueless, since, from the Pleistocene to the present day, there is no evidence of 

 the addition of one wild creature to the existing fauna with the exception of the common 



1 M. Gervais, the eminent writer of the ' Paleontologie et Zoologie Franchises,' comes to the same 

 conclusion, and for the same reasons, see edit. 1859. See also ' Nouvelles Recherches sur les Animaux 

 Vertebras,' 4to, 1869, p. 31. 



3 In a letter to the writer in September, 1871. 



3 'Quart. Geol. Journal,' 1869, p. 216. 



4 ' Antiquity of Man,' chapter i. 



5 Since this paragraph was written Sir Charles Lyell has withdrawn the term Post-pliocene, 

 ' Antiquity of Man,' 4th edit., 1873, Chapter 1. 



