4B& Geological Society. 



Srdly. Tlie 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 fresh water strata were 

 deposited we have no indications beyond those afforded by the area 

 of the strata themselves. Its breadth probably extended about SO 

 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 fresh-water 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 

 fresh-water deposits above the chalk, mixed and alternating with 

 others that are marine. 



ethl}'. 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 Specie? 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 

 of it which remain exhibit the upper portion of the head from 

 the nostrils backwards, in a very crushed state, a continuous series 

 of 52 vertebrsE, from the atlas to the commencement of the tail, 

 with nearly all the spinous processes; one scapula, and nearly the 

 whole of one fore paddle. The teeth (by which the four species 

 formerly described have been chiefly distinguished) are entirely 

 wanting in this individual; the author, however, considers it to be a 

 new species, from the following peculiarities of character. 



1. The length of each vertebra is uniformly three-fifths of its 

 breadth, a proportion not found to exist in any hitherto described 

 species. 



2. The paddle is of great size, and including the humerus must 

 have been equal to one-fifth of the length of the whole animal. 

 In the ulna or radius (it is difficult to say which) there is a notch 



on 



