CONTENTS. xi 



CHAPTER XIII. THE PORTLAND OOLITE PERIOD. 



Composition of the strata. Kimmeridge clay, Portland rocks. Sections at 

 Swindon, Bourton, and Great Hazeley. Fossils of the period. Reference 

 to Plate XV., representing fossils of the Kimmeridge clay and Portland 

 oolite. 



Figures and descriptions of Ichthyosaurus, Pleiosaurus, Plesiosaurus, Steneo- 



saurus, Dakosaurus, Ceteosaurus, Megalosaurus .. 324 



CHAPTER XIV. RETROSPECT OF THE OOLITIC SYSTEM. 



Tripartite series of rocks. Composition of the oolite. Figures of the structure 

 under the microscope.' The iron ores. Distribution of life. Change of the 

 forms of life in relation to time, illustrated by tables for Terebratulse, 

 Limae, Trigoniae, and Pholadomyse. Discussion of the doctrine of ' modifi- 

 cation by descent.' Comparison of the Stonesfield and Colly weston slate- 

 beds .. .. 392 



CHAPTER XV. PURBECK BEDS AND IRON-SAND OF SHOTOVER. 



Historical view. Ascent of Shotover Hill, with section in illustration. List of 

 the organic remains. Other localities of the Purbeck beds and iron-sands, 

 with fossils at several places. Reference to Plate XVI., containing section 

 and figures of fossils .. .. .. .. .. .. .. .. 410 



CHAPTER XVI. THE CRETACEOUS PERIOD. 



The component strata. Lower greensand and conglomerate traced. Faringdon 

 sponge-led. Culham clay-pit. Potton bone-bed. Catalogue of fossils of 

 the Cretaceous system of the district round Oxford . . . . . . . . 422 



CHAPTER XVII. THE EOCENE PERIOD. 



Waste of the chalk before the deposition of Eocene strata. Oyster-bed and 

 sections near Reading. Newbury. ' Grey- weathers ' or Sarsen stones. 

 Strata under London. Mylne's map. Thanet sand. Woolwich bed in the 

 lower part of the Vale of Thames .. .. .. .. .. .. 442 



CHAPTER XVIII. THE PLEISTOCENE PERIOD. 



Early elevations of land followed by great rising and falling after eocene period. 

 Valley deposits and Hill deposits contrasted. High level gravel on the Cots- 

 wolds, Chilterns, &c. Dr. Buckland's map and account of this gravel. 

 Mr. Hull's account of the distribution. Action of ice. Mr. Lucy's obser- 

 vations. General view. Low level gravel in the course of the Thames and 

 its feeders, at Yarnton, Oxford, Culham, Wittenham, &c. Composition of 

 the gravel beds. Occurrence of land and fresh- water shells in the gravel 



