THE CLASSIFICATION OF THE TERTIARY DEPOSITS. 127 
attempting to put this conclusion to the test, he availed himself 
of the valuable assistance which so able a conchologist as M. 
Deshayes was able to afford him. Lyell was so impressed by 
the distinctness of the Sicilian strata, which contain scarcely 
any but living forms, from those of the Subapennine hills, in 
which only about one half of the species can be identified with 
living ones, that he had already determined, before discussing 
the matter with Deshayes, to divide the Tertiary strata into 
four groups. M. Deshayes had, however, classed his shells in 
conformity with the facts which had been already made out by 
geologists into the three groups which we have already indi- 
cated. 
In the choice of names for the great divisions of the 
Tertiary series, which he was thus led to establish, Lyell 
determined to indicate the methods by which his results had 
been arrived at. After consultation with Dr. Whewell, he 
proposed to call the oldest strata, in which Deshayes’ tables 
showed only 42 forms out of 1238 to be still living (a pro- 
portion of three and a half per cent), the Eocene (r\wg, dawn, 
and kcllvoq, recent), as the beds may be regarded as exhibiting 
the dawn of the existing fauna of our seas. In the second 
group of Tertiary strata Deshayes’ tables showed 1021 species, 
of which 176 only were recent forms ; while in the third group 
it was found that more than one half the forms could be 
identified as still living ; hence Lyell called the second group 
Miocene (/ uziuv , minor, and kcllvoq, recent), as possessing a 
minority of living forms, and the third, the Pliocene (ttXelmv, 
major, and kmvoq, recent), as yielding a majority of living 
species. In his original classification Lyell was contented to 
employ these three terms only, dividing the Pliocene into Older 
and Newer. In 1839 he erected the Newer Pliocene into a 
distinct system, in accordance with his original views, giving 
it the name of Pleistocene (ttXzkttoq, most, and kcuvoq, recent) ; 
but as Edward Forbes and other writers employed this term in 
a sense quite distinct from that proposed by its author, and as 
synonymous with Post-Pliocene, its use, as indicating a division 
of the Tertiaries, was formally abandoned by Lyell. 
This nomenclature of the Tertiary strata which was proposed 
by Lyell has been frequently criticized, and is certainly open 
to the objection that it differs in its principles from that em- 
ployed in the case of the older rocks. Hence terms have been 
proposed by various authors as synonymous with Lyell’ s names, 
which, like the names of the older rocks, indicate their character- 
i I istic features or are derived from the localities in which the} r are 
. best developed. Thus some geologists prefer to call the Eocene 
the Nummulitic system, the Miocene the Falunian system, 
and the Pliocene the Subapennine system. But, on the other 
i 
