52 SUBDIVISIONS or [Ch. V. 



access, and the additions to the recent species in the cabinets 

 of conchologists in London, have been so great of late years, 

 that in many extensive genera the number of species has been 

 more than doubled. But as the greater part of these newly- 

 discovered shells have been brought from the Pacific and other 

 distant seas, it is probable that these accessions would not ma- 

 terially alter the results given in the tables,, and it must, at all 

 events, be remembered, that the only effect of such additional 

 information would be^ to increase the number of identifications 

 of recent with fossil species, while the proportional number of 

 analogues in the different periods might probably remain 

 nearly the same. 



SUBDIVISIONS OF THE TERTIARY EPOCH. 



Recent formations. We shall now proceed to consider the 

 subdivisions of tertiary strata which may be founded on the 

 results of a comparison of their respective fossils, and to give 

 names to the periods to which they each belong. The tertiary 

 epoch has been divided into three periods in the tables ; we 

 shall. however ; endeavour to establish four, all distinct from the 

 actual period, or that which has elapsed since the earth has been 

 tenanted by man. To the events of this latter era, which we 

 shall term the recent, we have exclusively confined ourselves in 

 the two preceding volumes. All sedimentary deposits, all vol- 

 canic rocks, in a word, every geological monument, whether 

 belonging to the animate or inanimate world, which appertains 

 to this epoch, may be termed recent. Some recent species, there- 

 fore, are found fossil in various tertiary periods, and, on the 

 other hand, others, like the Dodo, may be extinct, for it is suf- 

 ficient that they should once have coexisted with man, to make 

 them referriblc to this era. 



Some authors apply the term contemporaneous to all the 

 formations which have originated during the human epoch ; 

 but as the word is so frequently in use to express the synchro- 

 nous origin of distinct formations, it would be a source of great 

 inconvenience and ambiguity, if we were to attach to it a tech- 

 nical sense. 



