CONTENTS 
Synopsis promised, p. v. 
Contents of the Third Fasciculus, and Benefactors 
to the Museum, p. vi. 
Progress of Professor M°Coy’s Work, and causes 
of delay. Consequent injustice done to him. 
Index, by Mr Carter, pp. vii—ix. 
Error in the localities of the Graptolites from the 
Moffat group, p. x. 
Anatomical structure of Brachiopoda. A passage 
respecting Mr Woodward, in the Advertisement 
to the Second Fasciculus, explained, pp. xi. and 
xii. 
Mr Salter’s share in the work, p. xiii. 
Gradual elimination of the May Hill group, pp. 
xly. and xv. 
Great labour of Professor M°Coy, pp. xvi. xvii. 
True Geological nomenclature based on good phy- 
sical groups, and their subordinate fossils. Ex- 
amples, &c. pp. xvii.—xiv. 
Corrected Tabular View of the Primary or Paleozoic 
System of England.—Their Divisions, pp. xx.— 
XXV1. 
Pomfret Series, for European comparison, better 
than the Permian, p. xxvi. 
Difficulties in establishing the demarcations of the 
collective groups, pp. XXvii.—xxxi. 
1. <A good demarcation now established between 
the groups of the Cambrian and Silurian Series. 
2. The demarcation between the Upper Silurian 
and the Lower Devonian groups not unequivocal. 
Partly arising from the Lower Devonian groups 
of Scotland. Hypothetical explanation. 
3. A similar difficulty in separating the Devonian 
Series, of Devon and Cornwall, from the Car- 
boniferous. 
4. A like difficulty in separating the Carboniferous 
Series of the Northern Counties from the Pomfret 
(or Permian) Series, p. xxviii. 
Difficulty in defining the separation between the 
Pomfret (or Permian) Series and the Triassic. 
or 
OF THE 
INTRODUCTION. 
6. These difficulties do not materially affect our 
geographical nomenclature: but much caution is 
required in the application of the per-centage 
theory of Sir Charles Lyell. 
7. Examples of this application in determining 
the per centage of fossils common to Cambrian 
and Silurian Rocks, p. xxxi. 
Further remarks on the Cambrian Series and on 
the nomenclature of its groups. Difficulty in 
correctly analyzing the Cambrian Series, from the 
following four causes : 
1. From the vast thickness and complexity of the 
Series; and the almost entire absence of fossils 
from its lower groups, p. XXXil. 
2. From the prevalence of cleavage-planes. Series 
of facts and conclusions, p. xxxiii. Cleavage-planes 
the result of crystalline action. Sometimes ac- 
company a spherical structure. Theory of cleav- 
age-planes confirmed by certain phenomena in 
the structure of the Cornish granite, p.xxxiv. A 
second cleavage-plane, p. xxxv. Dip-joints and 
strike-joints explained on a mechanical theory of 
Mr Hopkins. Cleavage-planes and joints in the 
conglomerates of Trebennau, p. xxxvi. Mechani- 
cal theory of cleavage-planes rejected. 
3. From the prevalence of eruptive and stratified 
igneous rocks, pp. XXXV.—XXXvill. 
4. From the extraordinary dislocations and con- 
tortions. M. Elie de Beaumont’s theory of paral- 
lelism, p. xxxix. Of great value when applied 
under proper limitations. Examples, p. xl. 
May Hill Sandstone, its place and office in the 
general series, p. xli. Historical sketch of the 
gradual elaboration of the Cambrian series. Mis- 
take by the author of ‘Siluria” as to the sup- 
posed place of the Snowdon fossils, p. xli. 
Early difficulties in uniting the Upper Cambrian 
groups to the Lower Silurian, p. xliii. Attempts 
to overcome those difficulties, pp. xliv.—xlix. 
All such attempts failed so long as the ‘‘ Lower 
Silurian” sections were upheld and considered 
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