Book: The Ancient Life History of the Earth

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THE ANCIENT LIFE-HISTORY OF THE EARTH

A COMPREHENSIVE OUTLINE OF THE PRINCIPLES AND LEADING FACTS OF
PALAEONTOLOGICAL SCIENCE


BY H. ALLEYNE NICHOLSON

M.D., D.SC., M.A., PH. D. (GOeTT), F.R.S.E, F.L.S.

PROFESSOR OF NATURAL HISTORY IN THE UNIVERSITY OF ST ANDREWS




PREFACE.

The study of Palaeontology, or the science which is concerned
with the living beings which flourished upon the globe during
past periods of its history, may be pursued by two parallel but
essentially distinct paths. By the one method of inquiry, we may
study the anatomical characters and structure of the innumerable
extinct forms of life which lie buried in the rocks simply as
so many organisms, with but a slight and secondary reference
to the _time_ at which they lived. By the other method, fossil
animals are regarded principally as so many landmarks in the
ancient records of the world, and are studied _historically_
and as regards their relations to the chronological succession
of the strata in which they are entombed. In so doing, it is of
course impossible to wholly ignore their structural characters,
and their relationships with animals now living upon the earth;
but these points are held to occupy a subordinate place, and to
require nothing more than a comparatively general attention.

In a former work, the Author has endeavoured to furnish a summary
of the more important facts of Palaeontology regarded in its strictly
scientific aspect, as a mere department of the great science of
Biology. The present work, on the other hand, is an attempt to
treat Palaeontology more especially from its historical side, and
in its more intimate relations with Geology. In accordance with
this object, the introductory portion of the work is devoted to a
consideration of the general principles of Palaeontology, and the
bearings of this science upon various geological problems--such
as the mode of formation of the sedimentary rocks, the reactions
of living beings upon the crust of the earth, and the sequence
in time of the fossiliferous formations. The second portion of
the work deals exclusively with Historical Palaeontology, each
formation being considered separately, as regards its lithological
nature and subdivisions, its relations to other formations, its
geographical distribution, its mode of origin, and its characteristic
life-forms.

In the consideration of the characteristic fossils of each successive
period, a general account is given of their more important zoological
characters and their relations to living forms; but the technical
language of Zoology has been avoided, and the aid of illustrations
has been freely called into use. It may therefore be hoped that
the work may be found to be available for the purposes of both the
Geological and the Zoological student; since it is essentially an
outline of Historical Palaeontology, and the student of either of
the above-mentioned sciences must perforce possess some knowledge
of the last. Whilst primarily intended for students, it may be
added that the method of treatment adopted has been so far
untechnical as not to render the work useless to the general
reader who may desire to acquire some knowledge of a subject of
such vast and universal interest.

In carrying out the object which he has held before him, the
Author can hardly expect, from the nature of the materials with
which he has had to deal, that he has kept himself absolutely
clear of errors, both of omission and commission. The subject,
however, is one to which he has devoted the labour of many years,
both in studying the researches of others and in personal
investigations of his own; and he can only trust that such errors
as may exist will be found to belong chiefly to the former class,
and to be neither serious nor numerous. It need only be added
that the work is necessarily very limited in its scope, and that
the necessity of not assuming a thorough previous acquaintance
with Natural History in the reader has inexorably restricted its
range still further. The Author does not, therefore, profess to
have given more than a merely general outline of the subject; and
those who desire to obtain a more minute and detailed knowledge
of Palaeontology, must have recourse to other and more elaborate
treatises.

UNITED COLLEGE, ST ANDREWS.

October 2, 1876.




CONTENTS.


PART I.

PRINCIPLES OF PALAEONTOLOGY.


INTRODUCTION.

The general objects or geological science--The older theories of
catastrophistic and intermittent action--The more modern doctrines
of continuous and uniform action--Bearing of these doctrines
respectively on the origin or the existing terrestrial
order--Elements or truth in Catastrophism--General truth of the
doctrine of Continuity--Geological time.

CHAPTER I.

Definition of Palaeontology--Nature of Fossils--Different processes
of fossilisation.

CHAPTER II.

Aqueous and igneous rocks--General characters of the sedimentary
rocks--Mode or formation of the sedimentary rocks--Definition
of the term "formation"--Chief divisions of the aqueous
rocks--Mechanically-formed rocks, their characters and mode of
origin--Chemically and organically formed rocks--Calcareous
rocks--Chalk, its microscopic structure and mode of
formation--Limestone, varieties, structure, and origin--Phosphate
of lime--Concretions--Sulphate of lime--Silica and siliceous
deposits of various kinds--Greensands--Red clays--Carbon and
carbonaceous deposits.

CHAPTER III.

Chronological succession of the fossiliferous rocks--Tests or age
of strata--Value of Palaeontological evidence in stratigraphical
Geology--General sequence of the great formations.

CHAPTER IV.

The breaks in the palaeontological and geological record--Use of
the term "contemporaneous" as applied to groups of strata--General
sequence of strata and of life-forms interfered with by more or
less extensive gaps--Unconformability--Phenomena implied by
this--Causes of the imperfection of the palaeontological record.

CHAPTER V.

Conclusions to be drawn from fossils--Age of rocks--Mode of origin
of any fossiliferous bed--Fluviatile, lacustrine, and marine
deposits--Conclusions as to climate--Proofs of elevation and
subsidence of portions of the earth's crust derived from fossils.

CHAPTER VI.

The biological relations of fossils--Extinction of
life-forms--Geological range of different species--Persistent types
of life--Modern origin of existing animals and plants--Reference
of fossil forms to the existing primary divisions of the animal
kingdom--Departure of the older types of life from those now in
existence--Resemblance of the fossils of a given formation to
those of the formation next above and next below--Introduction
of new life-forms.


PART II.

HISTORICAL PALAEONTOLOGY.


CHAPTER VII.

The Laurentian and Huronian periods--General nature, divisions,
and geographical distribution of the Laurentian deposits--Lower
and Upper Laurentian--Reasons for believing that the Laurentian
rocks are not azoic based upon their containing limestones, beds of
oxide of iron, and graphite--The characters, chemical composition,
and minute structure of _Eozooen Canadense_--Comparison of _Eozooen_
with existing Foraminifera--_Archoeosphoerinoe_--Huronian
formation--Nature and distribution of Huronian deposits--Organic
remains of the Huronian--Literature.

CHAPTER VIII.

The Cambrian period--General succession of Cambrian deposits in
Wales--Lower Cambrian and Upper Cambrian--Cambrian deposits of
the continent of Europe and North American--Life of the Cambrian
period--Fucoids--Eophyton--Oldhamia--Sponges--Echinoderms--Annelides
--Crustaceans--Structure of Trilobites--Brachiopods--Pteropods,
Gasteropods, and Bivalves--Cephalopods--Literature.

CHAPTER IX.

The Lower Silurian period--The Silurian rocks generally--Limits
of Lower and Upper Silurian--General succession, subdivisions,
and characters of the Lower Silurian rocks of Wales--General
succession, subdivisions, and characters of the Lower Silurian
rocks of the North American continent--Life of the
period--Fucoids--Protozoa--Graptolites--Structure of
Graptolites--Corals--General structure of Corals--Crinoids--
Cystideans--General characters of Cystideans--Annelides--
Crustaceans--Polyzoa--Brachiopods--Bivalve and Univalve
Molluscs--Chambered Cephalopods--General characters of the
Cephalopoda--Conodonts.

CHAPTER X.

The Upper Silurian period--General succession of the Upper Silurian
deposits of Wales--Upper Silurian deposits of North America--Life
of the Upper Silurian--Plants--Protozoa--Graptolites--Corals--
Crinoids--General structure of Crinoids--Star-fishes--Annelides--
Crustaceans--Eurypterids--Polyzoa--Brachiopods--Structure of
Brachiopods--Bivalves and Univalves--Pteropods--Cephalopods--
Fishes--Silurian literature.

CHAPTER XI.

The Devonian period--Relations between the Old Red Sandstone
and the marine Devonian deposits--The Old Red Sandstone of
Scotland--The Devonian strata of Devonshire--Sequence and
subdivisions of the Devonian deposits of North America--Life
of the period--Plants--Protozoa--Corals-Crinoids--Pentremites--
Annelides--Crustaceans--Insects--Polyzoa--Brachiopods--Bivalves--
Univalves--Pteropods--Cephalopods--Fishes--General divisions of
the Fishes--Palaeontological evidence as to the independent
existence of the Devonian system as a distinct
formation--Literature.

CHAPTER XII.

The Carboniferous period--Relations of Carboniferous rocks to
Devonian--The Carboniferous Limestone or Sub-Carboniferous
series--The Millstone-grit and the Coal-measures--Life of the
period--Structure and mode of formation of Coal--Plants of the
Coal.

CHAPTER XIII.

Animal life of the Carboniferous period--Protozoa--Corals--
Crinoids--Pentremites--Structure of Pentremites--Echinoids--
Structure of Echinoidea--Annelides--Crustacea--Insects--
Arachnids--Myriapods--Polyzoa--Brachiopods--Bivalves and
Univalves--Cephalopods--Fishes--Labyrinthodont Amphibians--
Literature.

CHAPTER XIV.

The Permian period--General succession, characters, and mode
of formation of the Permian deposits--Life of the period--
Plants--Protozoa--Corals--Echinoderms--Annelides--Crustaceans--
Polyzoa--Brachiopods--Bivalves-Univalves--Pteropods--
Cephalopods--Fishes--Amphibians--Reptiles--Literature.

CHAPTER XV.

The Triassic period--General characters and subdivisions of the
Trias of the Continent of Europe and Britain--Trias of North
America--Life of the period--Plants--Echinoderms--Crustaceans--
Polyzoa--Brachiopods--Bivalves--Univalves--Cephalopods--
Intermixture of Palaeozoic with Mesozoic types of Molluscs--
Fishes--Amphibians--Reptiles--Supposed footprints of Birds--
Mammals--Literature.

CHAPTER XVI.

The Jurassic period--General sequence and subdivisions of the
Jurassic deposits in Britain--Jurassic rocks of North America--Life
of the period--Plants--Corals--Echinoderms--Crustaceans--Insects--
Brachiopods--Bivalves--Univalves-Pteropods--Tetrabranchiate
Cephalopods--Dibranchiate Cephalopods--Fishes--Reptiles--Birds--
Mammals--Literature.

CHAPTER XVII.

The Cretaceous period--General succession and subdivisions of
the Cretaceous rocks in Britain--Cretaceous rocks of North
America--Life of the period--Plants--Protozoa--Corals--Echinoderms--
Crustaceans--Polyzoa--Brachiopods--Bivalves--Univalves--
Tetrabranchiate and Dibranchiate Cephalopods--Fishes--Reptiles--
Birds--Literature.

CHAPTER XVIII.

The Eocene period--Relations between the Kainozoic and Mesozoic
rocks in Europe and in North America--Classification of the Tertiary
deposits--The sequence and subdivisions of the Eocene rocks of
Britain and France--Eocene strata of the United States--Life of the
period--Plants--Foraminifera--Corals--Echinoderms--Mollusca--Fishes--
Reptiles--Birds--Mammals.

CHAPTER XIX.

The Miocene period--Miocene strata of Britain--Of France--Of
Belgium--Of Austria--Of Switzerland--Of Germany--Of Greece--Of
India--Of North America--Of the Arctic regions--Life of the
period--Vegetation of the Miocene period--Foraminifera--Corals--
Echinoderms--Articulates--Mollusca--Fishes-Amphibians--Reptiles--
Mammals.

CHAPTER XX.

The Pliocene period--Pliocene deposits of Britain--Of Europe--Of
North America--Life of the period--Climate of the period as indicated
by the Invertebrate animals--The Pliocene Mammalia--Literature
relating to the Tertiary deposits and their fossils.

CHAPTER XXI.

The Post-Pliocene period--Division of the Quaternary deposits into
Post-Pliocene and Recent--Relations of the Post-Pliocene deposits
of the northern hemisphere to the "Glacial period"--Pre-Glacial
deposits--Glacial deposits--Arctic Mollusca in Glacial
beds--Post-Glacial deposits--Nature and mode of formation of
high-level and low-level gravels--Nature and mode of formation
of cavern-deposits--Kent's Cavern-Post--Pliocene deposits of
the southern hemisphere.

CHAPTER XXII.

Life of the Post-Pliocene period--Effect of the coming on and
departure of the Glacial period upon the animals inhabiting the
northern hemisphere--Birds of the Post-Pliocene--Mammalia of the
Post-Pliocene--Climate of the Post-Glacial period as deduced from
the Post-Glacial Mammals--Occurrence of the bones and implements
of Man in Post-Pliocene deposits in association with the remains
of extinct Mammalia--Literature relating to the Post-Pliocene
period.

CHAPTER XXIII.

The succession of life upon the globe--Gradual and successive
introduction of life-forms--What is meant by "lower" and "higher"
groups of animals and plants--Succession in time of the great
groups of animals in the main corresponding with their zoological
order--Identical phenomena in the vegetable kingdom--Persistent
types of life--High organisation of many early forms--Bearings
of Palaeontology on the general doctrine of Evolution.

APPENDIX.--Tabular view of the chief Divisions of the Animal Kingdom.

GLOSSARY.

INDEX.



LIST OF ILLUSTRATIONS

FIG.
1. Cast of _Trigonia longa_.
2. Microscopic section of the wood of a fossil Conifer.
3. Microscopic section of the wood of the Larch.
4. Section of Carboniferous strata, Kinghorn, Fife.
5. Diagram illustrating the formation of stratified deposits.
6. Microscopic section of a calcareous breccia.
7. Microscopic section of White Chalk.
8. Organisms in Atlantic Ooze.
9. Crinoidal marble.
10. Piece of Nummulitic limestone, Pyramids.
11. Microscopic section of Foraminiferal
limestone--Carboniferous, America.
12. Microscopic section of Lower Silurian limestone.
13. Microscopic section of oolitic limestone, Jurassic.
14. Microscopic section of oolitic limestone, Carboniferous.
15. Organisms in Barbadoes earth.
16. Organisms in Richmond earth.
17. Ideal section of the crust of the earth.
18. Unconformable junction of Chalk and Eocene rocks.
19. Erect trunk of a _Sigillaria_.
20. Diagrammatic section of the Laurentian rocks.
21. Microscopic section of Laurentian limestone.
22. Fragment of a mass of _Eozooen Canadense_.
23. Diagram illustrating the structure of _Eozooen_.
24. Microscopic section of _Eozooen Canadense_.
25. _Nonionina_ and _Gromia_.
26. Group of shells of living _Foraminifera_.
27. Diagrammatic section of Cambrian strata.
28. _Eophyton Linneanum_.
29. _Oldhamia antiqua_.
30. _Scolithus Canadensis_.
31. Group of Cambrian Trilobites.
32. Group of characteristic Cambrian fossils.
33. Fragment of _Dictyonema sociale_.
34. Generalised section of the Lower Silurian rocks
of Wales.
35. Generalised section of the Lower Silurian rocks
of North America.
36. _Licrophycus Ottawaensis_.
37. _Astylospongia proemorsa_.
38. _Stromatopora rugosa_.
39. _Dichograptus octobrachiatus_.
40. _Didymograptus divaricatus_.
41. _Diplograptus pristis_.
42. _Phyllograptus typus_.
43. _Zaphrentis Stokesi_.
44. _Strombodes pentagonus_.
45. _Columnaria alveolata_.
46. Group of Cystideans.
47. Group of Lower Silurian Crustaceans.
48. _Ptilodictya falciformis_.
49. _Ptilodictya Schafferi_.
50. Group of Lower Silurian Brachiopods.
51. Group of Lower Silurian Brachiopods.
52. _Murchisonia gracilis_.
53. _Bellerophon argo_.
54. _Maclurea crenulata_.
55. _Orthoceras crebriseptum_.
56. Restoration of _Orthoceras_.
57. Generalised section of the Upper Silurian rocks.
58. _Monograptus priodon_.
59. _Halysites catenularia_ and _H. agglomerata_.
60. Group of Upper Silurian Star-fishes.
61. _Protaster Sedgwickii_.
62. Group of Upper Silurian Crinoids.
63. _Planolites vulgaris_.
64. Group of Upper Silurian Trilobites.
65. _Pterygotus Anglicus_.
66. Group of Upper Silurian _Polyzoa_.
67. _Spirifera hysterica_.
68. Group of Upper Silurian Brachiopods.
69. Group of Upper Silurian Brachiopods.
70. _Pentamerus Knightii_.
71. _Cardiola interrupta, C. fibrosa_, and _Pterinoea
subfalcata_.
72. Group of Upper Silurian Univalves.
73. _Tentaculites ornatus_.
74. _Pteraspis Banksii_.
75. _Onchus tenuistriatus_ and _Thelodus_.
76. Generalised section of the Devonian rocks of North America.
77. _Psilophyton princeps_.
78. _Prototaxites Logani_.
79. _Stromatopora tuberculata_.
80. _Cystiphyllum vesiculosum_.
81. _Zaphrentis cornicula_.
82. _Heliophyllum exiguum_.
83. _Crepidophyllum Archiaci_.
84. _Favosites Gothlandica_.
85. _Favosites hemisphoerica_.
86. _Spirorbis omphalodes_ and _S. Arkonensis_.
87. _Spirorbis laxus_ and _S. Spinulifera_.
88. Group of Devonian Trilobites.
89. Wing of _Platephemera antiqua_.
90. _Clathropora intertexta_.
91. _Ceriopora Hamiltonensis_.
92. _Fenestella magnifica_.
93. _Retepora Phillipsi_.
94. _Fenestella cribrosa_.
95. _Spirifera sculptilis_.
96. _Spirifera mucronata_.
97. _Atrypa reticularis_.
98. _Strophomena rhomboidalis_.
99. _Platyceras dumosum_.
100. _Conularia ornata_.
101. _Clymenia Sedgwickii_.
102. Group of Fishes from the Devonian rocks of North America.
103. _Cephalaspis Lyellii_.
104. _Pterichthys cornutus_.
105. _Polypterus_ and _Osteolepis_.
106. _Holoptychius nobilissimus_.
107. Generalised section of the Carboniferous rocks of the
North of England.
108. _Odontopteris Schlotheimii_.
109. _Calamites cannoeformis_.
110. _Lepidodendron Sternbergii_.
111. _Sigillaria Groeseri_.
112. _Stigmaria ficoides_.
113. _Trigonocarpum ovatum_.
114. Microscopic section of Foraminiferal
limestone--Carboniferous, North America.
115. _Fusulina cylindrica_.
116. Group of Carboniferous Corals.
117. _Platycrinus tricontadactylus_.
118. _Pentremites pyriformis_ and _P. conoideus_.
119. _Archoeocidaris ellipticus_.
120. _Spirorbis Carbonarius_.
121. _Prestwichia rotundata_.
122. Group of Carboniferous Crustaceans.
123. _Cyclophthalmus senior_.
124. _Xylobius Sigillarioe_.
125. _Haplophlebium Barnesi_.
126. Group of Carboniferous _Polyzoa_.
127. Group of Carboniferous _Brachiopoda_.
128. _Pupa vetusta_.
129. _Goniatites Fossoe_.
130. _Amblypterus macropterus_.
131. _Cochliodus contortus_.
132. _Anthracosaurus Russelli_.
133. Generalised section of the Permian rocks.
134. _Walchia piniformis_.
135. Group of Permian _Brachiopods_.
136. _Arca antiqua_.
137. _Platysomus gibbosus_.
138. _Protorosaurus Speneri_.
139. Generalised section of the Triassic rocks.
140. _Zamia spiralis_.
141. Triassic Conifers and Cycads.
142. _Encrinus liliiformis_.
143. _Aspidura loricata_.
144. Group of Triassic Bivalves.
145. _Ceratites nodosus_.
146. Tooth of _Ceratodus serratus_ and _C. Altus_.
147. _Ceratodus Fosteri_.
148. Footprints of _Cheirotherium_.
149. Section of tooth of _Labyrinthodont_.
150. Skull of _Mastodonsaurus_.
151. Skull of _Rhynchosaurus_.
152. _Belodon_, _Nothosaurus_, _Paloeosaurus_, &c.
153. _Placodus gigas_.
154. Skulls of _Dicynodon_ and _Oudenodon_.
155. Supposed footprint of Bird, from the Trias of Connecticut.
156. Lower jaw of _Dromatherium sylvestre_.
157. Molar tooth of _Microlestes antiquus_.
158. _Myrmecobius fasciatus_.
159. Generalised section of the Jurassic rocks.
160. _Mantellia megalophylla_.
161. _Thecosmilia annularis_.
162. _Pentacrinus fasciculosus_.
163. _Hemicidaris crenularis_.
164. _Eryon arctiformis_.
165. Group of Jurassic Brachiopods.
166. _Ostrea Marshii_.
167. _Gryphoea incurva_
168. _Diceras arietina_.
169. _Nerinoea Goodhallii_.
170. _Ammonites Humphresianus_.
171. _Ammonites bifrons_.
172. _Beloteuthis subcostata_.
173. Belemnite restored; diagram of Belemnite; _Belemnites
canaliculata_.
174. _Tetragonolepis_.
175. _Acrodus nobilis_.
176. _Ichthyosaurus communis_.
177. _Plesiosaurus dolichodeirus_.
178. _Pterodactylus crassirostris_.
179. _Ramphorhynchus Bucklandi_, restored.
180. Skull of _Megalosaurus_.
181. _Archoeopteryx macrura_.
182. _Archoeopteryx, restored_.
183. Jaw of _Amphitherium Prevostii_.
184. Jaws of Oolitic Mammals.
185. Generalised section of the Cretaceous rocks.
186. Cretaceous Angiosperms.
187. _Rotalia Boueana_.
188. _Siphonia ficus_.
189. _Ventriculites simplex_.
190. _Synhelia Sharpeana_.
191. _Galerites albogalerus_.
192. _Discoidea cylindrica_.
193. _Escharina Oceani_.
194. _Terebratella Astieriana_.
195. _Crania Ignabergensis_.
196. _Ostrea Couloni_.
197. _Spondylus spinosus_.
198. _Inoceramus sulcatus_.
199. _Hippurites Toucasiana_.
200. _Voluta elongata_.
201. _Nautilus Danicus_.
202. _Ancyloceras Matheronianus_.
203. _Turrilites catenatus_
204. Forms of Cretaceous _Ammonitidoe_.
205. _Belemnitella mucronata_.
206. Tooth of _Hybodus_.
207. Fin-spine of _Hybodus_.
208. _Beryx Lewesiensis_ and _Osmeroides Mantelli_.
209. Teeth of _Iguanodon_.
210. Skull of _Mosasaurus Camperi_.
211. _Chelone Benstedi_.
212. Jaws and vertebrae of _Odontornithes_.
213. Fruit of _Nipadites_.
214. _Nummulina loevigata_.
215. _Turbinolia sulcata_.
216. _Cardita planicosta_.
217. _Typhis tubifer_.
218. _Cyproea elegans_.
219. _Cerithium hexagonum_.
220. _Limnoea pyramidalis_.
221. _Physa columnaris_.
222. _Cyclostoma Arnoudii_.
223. _Rhombus minimus_.
224. _Otodus obliquus_.
225. _Myliobatis Edwardsii_.
226. Upper jaw of Alligator.
227. Skull of _Odontopteryx toliapicus_.
228. _Zeuglodon cetoides_.
229. _Paloeotherium magnum_, restored.
230. Feet of _Equidoe_.
231. _Anoplothelium commune_.
232. Skull of _Dinoceras mirabilis_.
233. _Vespertilio Parisiensis_.
234. Miocene Palms.
235. _Platanus aceroides_.
236. _Cinnamomum polymorphum_.
237. _Textularia Meyeriana_.
238. _Scutella subrotunda_.
239. _Hyalea Orbignyana_.
240. Tooth of _Oxyrhina_.
241. Tooth of _Carcharodon_.
242. _Andrias Scheuchzeri_.
243. Skull of _Brontotherium ingens_.
244, _Hippopotamus Sivalensis_.
245. Skull of _Sivatherium_.
246. Skull of _Deinotherium_.
247. Tooth of _Elephas planfrons_ and of _Mastodon
Sivalensis_.
248. Jaw of _Pliopithecus_.
249. _Rhinoceros Etruscus_ and _R. megarhinus_.
250. Molar tooth of _Mastodon Arvernensis_.
251. Molar tooth of _Etephas meridionalis_.
252. Molar tooth of _Elephas antiquus_.
253. Skull and tooth of _Machairodus cultridens_.
254. _Pecten Islandicus_.
255. Diagram of high-level and low-level gravels.
256. Diagrammatic section of Cave.
257. _Dinornis elephantopus_.
258. Skull of _Diprotodon_.
259. Skull of _Thylacoleo_.
260. Skeleton of _Megatherium_.
261. Skeleton of _Mylodon_.
262. _Glyptodon clavipes_.
263. Skull of _Rhinoceros tichorhinus_.
264. Skeleton of _Cervus megaceros_.
265. Skull of _Bos primigenius_.
266. Skeleton of Mammoth.
267. Molar tooth of Mammoth.
268. Skull of _Ursus speloeus_.
269. Skull of _Hyoena speloea_.
270. Lower jaw of _Trogontherium Cuvieri_.



PART I.

PRINCIPLES OF PALAEONTOLOGY.




INTRODUCTION.

THE LAWS OF GEOLOGICAL ACTION.

Under the general title of "Geology" are usually included at
least two distinct branches of inquiry, allied to one another in
the closest manner, and yet so distinct as to be largely capable
of separate study. _Geology_,[1] in its strict sense, is the
science which is concerned with the investigation of the materials
which compose the earth, the methods in which those materials
have been arranged, and the causes and modes of origin of these
arrangements. In this limited aspect, Geology is nothing more than
the Physical Geography of the past, just as Physical Geography
is the Geology of to-day; and though it has to call in the aid
of Physics, Astronomy, Mineralogy, Chemistry, and other allies
more remote, it is in itself a perfectly distinct and individual
study. One has, however, only to cross the threshold of Geology
to discover that the field and scope of the science cannot be
thus rigidly limited to purely physical problems. The study of
the physical development of the earth throughout past ages brings
us at once in contact with the forms of animal and vegetable
life which peopled its surface in bygone epochs, and it is found
impossible adequately to comprehend the former, unless we possess
some knowledge of the latter. However great its physical advances
may be, Geology remains imperfect till it is wedded with
Palaeontology,[2] a study which essentially belongs to the vast
complex of the Biological Sciences, but at the same time has its
strictly geological side. Dealing, as it does, wholly with the
consideration of such living beings as do not belong exclusively
to the present order of things, Palaeontology is, in reality, a
branch of Natural History, and may be regarded as substantially
the Zoology and Botany of the past. It is the ancient life-history
of the earth, as revealed to us by the labours of palaeontologists,
with which we have mainly to do here; but before entering upon
this, there are some general questions, affecting Geology and
Palaeontology alike, which may be very briefly discussed.

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