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 escarpments--Rise and denudation of the strata gradual--Ridges formed by harder, valleys by softer beds--Why no alluvium, or wreck of the chalk, in the central district of the Weald--At what periods the Weald valley was denuded--Land has most prevailed where denudation has been greatest--Elephant bed, Brighton 238 CHAPTER XX. OOLITE AND LIAS. Subdivisions of the Oolitic or Jurassic group--Physical geography of the Oolite in England and France--Upper Oolite--Portland stone and fossils--Lithographic stone of Solenhofen--Middle Oolite, coral rag--Zoophytes--Nerinaean limestone--Diceras limestone--Oxford clay, Ammonites and Belemnites--Lower Oolite, Crinoideans--Great Oolite and Bradford clay--Stonesfield slate--Fossil mammalia, placental and marsupial--Resemblance to an Australian fauna--Doctrine of progressive development--Collyweston slates--Yorkshire Oolitic coal-field--Brora coal--Inferior Oolite and fossils 257 CHAPTER XXI. OOLITE AND LIAS--_continued_. Mineral character of Lias--Name of Gryphite limestone--Fossil shells and fish--Ichthyodorulites--Reptiles of the Lias--Ichthyosaur and Plesiosaur--Marine Reptile of the Galapagos Islands--Sudden destruction and burial of fossil animals in Lias--Fluvio-marine beds in Gloucestershire and insect limestone--Origin of the Oolite and Lias, and of alternating calcareous and argillaceous formations--Oolitic coal-field of Virginia, in the United States 273 CHAPTER XXII. TRIAS OR NEW RED SANDSTONE GROUP. Distinction between New and Old Red Sandstone--Between Upper and Lower New Red--The Trias and its three divisions--Most largely developed in Germany--Keuper and its fossils--Muschelkalk--Fossil plants of Bunter--Triassic group in England--Bone-bed of Axmouth and Aust--Red Sandstone of Warwickshire and Cheshire--Footsteps of _Chirotherium_ in England and Germany--Osteology of the _Labyrinthodon_--Identification of this Batrachian with the Chirotherium--Origin of Red Sandstone and rock-salt--Hypothesis of saline volcanic exhalations--Theory of the precipitation of salt from inland lakes or lagoons--Saltness of the Red Sea--New Red Sandstone in the United States--Fossil footprints of birds and reptiles in the Valley of the Connecticut--Antiquity of the Red Sandstone containing them 286 CHAPTER XXIII. PERMIAN OR MAGNESIAN LIMESTONE GROUP.