22 
NEWEST TERTIARY STRATA. 
[Ch. II. 
remains which characterize each of the three successive 
periods above alluded to, approximate more nearly to the 
assemblage of species now existing, in proportion as their 
origin is less remote from our own era, or, in other words, the 
recent species are always more numerous, and the extinct more 
rare, in proportion to the low antiquity of the formation. But 
the discordance between the state of the organic world indi- 
cated by the fossils of the Subapennine beds and the actual 
state of things is still considerable, and we naturally ask, are 
there no monuments of an intervening period ? — no evidences of 
a gradual passage from one condition of the animate creation 
to that which now prevails, and which differs so widely ? 
It will appear in the sequel, that such monuments are not 
wanting, and that there are marine strata entering into the 
composition of extensive districts, and of hills of no trifling 
height, which contain the exuviae of testacea and zoophytes, 
hardly distinguishable, as a group, from those now peopling 
the neighbouring seas. Thus the line of demarcation between 
the actual period and that immediately antecedent, is quite 
evanescent, and the newest members of the tertiary series will 
be often found to blend with the formations of the historical 
era. 
In Europe, these modern strata have been found in the dis- 
trict around Naples, in the territory of Otranto and Calabria, 
and more particularly in the island of Sicily ; and the bare 
enumeration of these localities cannot fail to remind the reader, 
that they belong to regions where the volcano and the earth- 
quake are now active, and where we might have anticipated 
the discovery of emphatic proofs, that the conversion of sea 
into land had been of frequent occurrence at very modern 
periods. 
