Ch. V.] 
THE TERTIARY EPOCH. 
53 
We may sometimes prove, that certain strata belong to the 
recent period by aid of historical evidence, as parts of the delta 
of the Po, Rhone, and Nile, for example; at other times, by 
discovering imbedded remains of man or his works ; but when 
we have no evidence of this kind, and we hesitate whether to 
ascribe a particular deposit to the recent era, or that immedi- 
ately preceding, we must generally incline to refer it to the 
latter, for it will appear in the sequel, that the changes of the 
historical era are quite insignificant when contrasted with those 
even of the newest tertiary period. 
Newer Pliocene period. — This most modern of the four 
subdivisions of the whole tertiary epoch, we propose to call the 
Newer Pliocene, which, together with the Older Pliocene, con- 
stitute one group in the annexed tables of M. Deshayes. 
We derive the term Pliocene from wAejwv, major, and y.ccivos, 
recens, as the major part of the fossil testacea of this epoch are 
referrible to recent species*. Whether in all cases there may 
hereafter prove to be an absolute preponderance of recent 
species, in every group of strata assigned to this period in the 
tables, is very doubtful; but the proportion of living species, 
where least considerable, usually approaches to one-half of the 
total number, and appears always to exceed a third ; and as our 
acquaintance with the testacea of the Mediterranean, and some 
other seas, increases, it is probable that a greater proportion 
will be identified. 
* In the terms Pliocene, Miocene, and Eocene, the Greek diphthongs ei and 
ai are changed into the vowels i and e, in conformity with the idiom of our lan- 
guage. Thus we have Encenia, an inaugural ceremony, derived from iv and 
xuivo;, recens; and as examples of the conversion of ei into i, we have icosahedron. 
I have heen much indebted to my friend, the Rev. W. Whewell, for assisting 
me in inventing and anglicizing these terms, and I sincerely wish that the numer- 
ous foreign diphthongs, barbarous terminations, and Latin plurals, which have 
been so plentifully introduced of late years into our scientific language, had been 
avoided as successfully as they are by French Naturalists, and as they were by the 
earlier English writers, when our language was more flexible than it is now. But 
while I commend the French for accommodating foreign terms to the structure of 
their own language, I must confess that no naturalists have been more unscholar- 
like in their mode of fabricating Greek derivatives and compounds, many of the 
latter being a bastard offspring of Greek and Latin. 
