52 
SUBDIVISIONS OF 
[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 referrible 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. 
