221 



2ndly. Some part of the bottom of this sea appears for a certain 

 time to have become dry land, and whilst in that state, to have 

 been covered with a forest of large coniferous trees and cycadeoi- 

 deous plants which indicate a warm climate. We have a measure 

 of the duration of this forest in the black earth which is accu- 

 mulated to the thickness of more than a foot from the wreck of 

 its vegetation : the regular and uniform preservation of this thin 

 bed of black earth over a distance of many miles, shows that the 

 change to the next state of things was not accompanied by any vio- 

 lent denudation or rush of waters, since the trees that lie prostrate 

 on this black earth would have been swept away by any such vio- 

 lent catastrophe. Dr. Buckland has found this same black earth 

 on the surface of the Portland stone near Thame in Oxfordshire. 

 It has also been found by Dr. Fitton in the Boulonnois. 



3rdly. The dry land on which this^forest grew, in Dorsetshire, be- 

 came converted to something like an estuary, in which the lowest 

 deposits contain freshwater shells, succeeded by a thick bed of 

 oyster shells ; and above the oyster bed, by strata containing an ad- 

 mixture of freshwater shells with shells that are marine. This fresh- 

 water formation, including both the Purbeck and the Wealden strata, 

 extends with certain interruptions from Upway on the N. of Wey- 

 mouth to the E. extremity of Purbeck, and reappears in the Isle of 

 Wight and the Weald of Sussex and Kent ; but of the boundaries 

 of the estuary or estuaries in which these freshwater strata were 

 deposited we have no indications beyond those afforded by the area 

 of the strata themselves. Its breadth probably extended about 30 

 miles from Purbeck to Tisbury on the west of Salisbury, across 

 the intermediate portion of Dorset and Wilts, which is now covered 

 up with chalk. 



4thly. We have a return of the sea over the estuary, and in this 

 sea an accumulation of the successive and thick marine deposits 

 which constitute the greensand and chalk formations. 



5thly. Although no freshwater formations occur in the tertiary 

 strata above the chalk on the coast of Dorset, we have on the 

 adjacent coast of Hants and the Isle of Wight, a re-appearance of 

 freshwater deposits above the chalk, mixed and alternating with 

 others that are mai'ine. 



6thty. All these deposits appear to have been succeeded by 

 powerful convulsions, producing elevation and depression of the 

 strata, intersecting them with tremendous faults, and followed by an 

 inundation competent to excavate deep valleys of denudation, and 

 to overspread the country with diluvial gravel. 



7thly. This inundation has been succeeded by a state of tran- 

 quillity, which has continued to the present hour. 



A paper entitled " Description of a New Species of Ichthyosau • 

 rus," by Daniel Sharpe, Esq., F.G.S., was then read. 



This specimen of Ichthyosaurus was found in a quarry of lias lime" 

 stone about four miles from Stratford-upon-Avon. The whole length 

 of the animal must probably have been about seven feet ; the parts 



