CONTENTS. x i 



in Chalk — Siliceous Diatoinaceas of the Atlantic — By what intermittent action 

 the alternate layers of white chalk and flint may have been caused — Pot- 

 stones of Horstead — Isolated pebbles of quartz and foreign rocks in chalk — 

 Fossils of the Upper Cretaceous rocks — Eckinoderms, Mollusca, Bryozoa, 

 Sponges — Upper Greensand and Gault — Blackdown beds — Fiora of the Upper 

 Cretaceous period — Fossil plants of Aix-la-Ckapelle — Large proportion of Dico- 

 tyledonous Angiosperms — Their coexistence with large extinct genera of reptiles 

 — Chalk of South of Europe — Hippurite limestone — Cretaceous rocks of the 

 United States, ------- page 312 



Chapter XYIII. — Lower Cretaceous and Wealdert Formations. 



Lower Greensand — Term "Neocomian" — Atherfield section, Isle of Wight — Fos- 

 sils of Lower Greensand — Palaeontological relations of the Upper and Lower Cre- 

 taceous strata — Wealden Formation— Freshwater strata intercalated between two 

 marine groups — Weald Clay and Hastings Sand — Tunbridge rocks — Fossil shells, 

 fish, and plants of Wealden — Their relation to the Cretaceous type — Geographi- 

 cal extent of Wealden — Movements in the earth's crust to which the Wealden 

 owed its origin and submergence, ------ 341 



Chapter XIX. — Denudation of the Chalk and Wealden. 



Physical geography of certain districts composed of Cretaceous and Wealden strata 

 — Lines of inland chalk-cliffs on the Seine in Normandy — Outstanding pillars and 

 needles of chalk — Denudation of the chalk and Wealden in Surrey, Kent, and 

 Sussex — Chalk once continuous from the North to the South Downs — Anticlinal 

 axis and parallel ridges — Longitudinal and transverse valleys — Chalk escarp- 

 ments — Rise and denudation of the strata gradual — Ridges formed by harder, 

 valleys by softer beds — At what periods the Weald Yalley was denuded — Why no 

 alluvium, or wreck of the chalk, in the central district of the Weald — Successive 

 periods of marine denudation — The latest. of these posterior to the Upper Mio- 

 cene era — Elephant-bed, Brighton — Sangatte Cliff — The great escarpments and 

 transverse valleys of the chalk mainly due to the waves and tides of the sea — 

 Paroxysmal causes unnecessary for explaining the external configuration of the 

 Wealden, - - - 353 



Chapter XX. — Jurassic Group — Purbeck Beds and Oolite. 



The Purbeck beds a member of the Jurassic group — Subdivisions of that group — 

 Physical geography of the Oolite in England and France — Upper Oolite — Purbeck 

 beds — New genera of fossil mammalia in the Middle Purbeck of Dorsetshire — 

 Dirt-bed or ancient soil — Fossils of the Purbeck beds — Portland stone and fossils 

 — Lithographic stone of Solenhofen — Archaoopteryx — Middle Oolite — Coral rag — 

 Zoophytes — Nerinsean limestone — Diceras limestone — Oxford clay, Ammonites, 

 and Belemnites — Kelloway Rock — Lower Oolite, Crinoideans — Great Oolite and 

 Bradford clay — Stonesfield slate — Fossil mammalia — Resemblance to an Austra- 

 lian fauna — Northamptonshire slates — Yorkshire Oolitic coal-field — Brora coal — 

 Fuller's earth — Inferior Oolite and fossils — Paloeontological relations of the sev- 

 eral subdivisions of the Oolitic group, ----- 377 



Chapter XXI. — Jurassic Group, continued — Lias. 



Mineral character of Lias — Numerous successive Zones in the Lias, marked by dis- 

 tinct fossils, without unconformity in the stratification, or change in the mineral 

 character of the deposits — Name of Gryphite limestone — Fossil shells and fish — 

 Radiata — Ichthyodorulites — Reptiles of the Lias — Ichthyosaur and Plesiosaur — 



