56 Geological Society. 



at Burham, which is situated near the banks of the Medway, between 

 Chatham and Maidstone. The specimen discovered consists of the 

 carapace or dorsal shell, six inches in length and nearly four inches 

 in breadth, with some of the sternal plates, vertebrae, eight ribs on 

 each side of the dorsal ridge, a border of marginal plates, and one 

 of the coracoid bones. It is adherent to a block of chalk by the 

 external surface of the sternal plates. The marginal plates are 

 joined to each other by finely indented sutures, and bear the impress 

 of the horny scales or tortoise-shell with which they were originally 

 covered. The expanded ribs are united together throughout the 

 proximal half of their length, and gradually taper to their marginal 

 extremities, which are protected by the plates of the osseous border. 

 Mr. Bell considers the species to which it belonged as being closely 

 allied in form to the common European Emys, and as possessing a 

 truly fluviatile or lacustrine character. The plates of the plastron, 

 however, as also the coracoid bone, resemble more the corresponding 

 bones of marine than of freshwater turtles. 



GEOLOGICAL SOCIETY. 



Dec. 16, 1840. — A paper " On the Relative Connection of the 

 Eastern and Western Chalk Denudations," by P. J. Martin, Esq., 

 F.G.S., was read. 



The author advances this as the first of a series of papers on the 

 construction of that part of the country usually considered as 

 appertaining to the great chalk denudation of the Weald, or more 

 properly, the upburst of the secondary formations between the 

 tertiary of the respective basins of London and Hampshire. 



In venturing on this field of inquiry, he professes also to take up 

 the subject where it was left by him in two former memoirs, one 

 published in 1 828 under the title of a ' Geological Memoir of Western 

 Sussex, with some Observations on Chalk Basins and the Weald 

 Denudation,' the other in the ' Philosophical Magazine ' for Fe- 

 bruary 1829 ; and to extend the number of demonstrative facts that 

 bear upon the theory of denudation by disruptive violence and con- 

 temporaneous aqueous abrasion, there brought forward as a corollary 

 to Dr. Buckland's theory of ' Valleys of Elevation.' 



In pursuance of this object, he begins by an examination into the 

 arrangement of the great chalk dome of Hampshire and Wiltshire, — 

 the Patria of the chalk of Pennant and Conybeare ; its anticlinal 

 lines of disturbance or upheaval, and their connections with those 

 of the Weald and the smaller western denudations of Pewsey, War- 

 dour and Warminster. 



He finds that six great anticlinal lines are the main instruments 

 of the upbearing of this abraded chalk ; that the three which 

 characterize the smaller anticlinal western valleys are projected 

 onward, and in a manner decussate three others which emanate 

 from the western extremity of the greater valley of the Weald, the 

 vale of Wolmar Forest, from whence he starts his inquiry ; and that 

 these lines do not inosculate or enter into each other ; approxima- 

 ting, indeed, but little in any part of their course ; severally dying 



