x CONTENTS. 



deposits — The value and nature of palaeontological evidence in 

 stratigraphical geology — Relative value of different groups of 

 organisms as tests of the age of strata — Contemporaneity and 

 homotaxis — General sequence of phenomena at the close of 

 each geological period — Migrations — Differences between the 

 organic remains of known contemporaneous deposits — Geologi- 

 cal continuity— Stratigraphical breaks and their general causes 

 — Life-zones — The doctrine of " colonies," 36-62 



CHAPTER IV. 



Causes of the imperfection of the palaeontological record — Causes 

 of the absence of certain animals as fossils — Unrepresented 

 time — Geological breaks — Sequence of phenomena indicated by 

 unconformity — Thinning-out of beds — Deep-sea deposits, and 

 their supposed absence from the stratified series — Disappear- 

 ance of fossils, 63-76 



CHAPTER V. 



Conclusions to be drawn from fossils — Age of rocks — Mode of origin 

 of any fossiliferous bed — Fluviatile, lacustrine, and marine de- 

 posits — Conclusions as to climate — Existence of climatic zones 

 in past time, 77-8i 



CHAPTER VI. 



Relations of Palaeontology to Geology — Relations of Palaeontology 

 to Zoology and Botany — Methods of palaeontological investiga- 

 tion — Correlation of organs — Classification of the Animal King- 

 dom — Primary morphological types — Impossibility of a linear 

 classification — The term " species " in Palaeontology — Tabular 

 view of the divisions of the Animal Kingdom, . . . 82-95 



CHAPTER VII. 



The evolution of organic types in time — Earlier theories on the sub- 

 ject — The primordial types of life — The introduction of new 

 species — The abrupt appearance of new species — The relative 

 persistence of species in time — The relative range of morpho- 

 logical types in space — The extinction of morphological types 

 — The evolution of morphological types from pre-existing forms 

 — Comprehensive types — Generalised character of many fossil 

 animals — Embryonal types — General palaeontological evidence 

 in favour of the evolution of species from pre-existing species — 

 General progression of organic types — The absence of closely- 

 graduated transitional forms between allied morphological 

 types, 96-105 



