XX 
CONTENTS, 
CHAPTER IV. 
PAGE 
Chronological relations of mineral masses the first object in geological 
classification — Superposition, proof of more recent origin — Exceptions in re- 
gard to volcanic rocks — Relative age proved by included fragments of older 
rocks — Proofs of contemporaneous origin derived from mineral characters — 
Variations to which these characters are liable — Recurrence of distinct rocks 
at successive periods — Proofs of contemporaneous origin derived from organic 
remains — Zoological provinces are of limited extent, yet spread over wider 
areas than homogeneous mineral deposits — Different modes whereby dis- 
similar mineral masses and distinct groups of species may be proved to have 
been contemporaneous . . ... . .35 
CHAPTER V. 
Classification of tertiary formations in chronological order — Comparative 
value of different classes of organic remains — Fossil remains of testacea the 
most important, — Necessity of accurately determining species — Tables of shells 
by M. Deshayes — Four subdivisions of the Tertiary epoch — Recent for- 
mations — Newer Pliocene period — Older Pliocene period — Miocene period 
—Eocene period — The distinct zoological characters of these periods may not 
imply sudden changes in the animate creation — The recent strata form a 
common point of departure iu distant regions — Numerical proportion of 
recent species of shells in different tertiary periods — Mammiferous remains 
of the successive tertiary eras — Synoptical Table of Recent and Tertiary 
formations ....... 45 
CHAPTER VI. 
Newer Pliocene formations—Reasons for considering in the first place the 
more modern periods — Geological structure of Sicily — Formations of the 
Val di Noto of newer Pliocene period — Divisible into three groups — Great 
limestone — Schistose and arenaceous limestone— Blue marl with shells — 
Strata subjacent to the above — Volcanic rocks of the Val di Noto — Dikes — 
Tuffs and Peperinos — Volcanic conglomerates — Proofs of long intervals 
between volcanic eruptions— Dip and direction of newer Pliocene strata 
of Sicily . . . . . . . .62 
CHAPTER VII. 
Marine and volcanic formations at the base of Etna — Their connexion 
with the strata of the Val di Noto — Bay of Trezza — Cyclopian isles — Fossil 
shells of recent species — Basalt and altered rocks in the Isle of Cyclops — 
