326 Dr. FiTTON on the Strata below the Chalk. 



or Lake-Erie. The lacustrine deposits, again, would be occasionally diver- 

 sified by the presence of the products of estuaries, such as those of the St. 

 Lawrence and of other rivers around Hudson's Bay and the north-east coast 

 of America; and in these we should probably find, along with the species of 

 shells which usually inhabit the mouths of large rivers and the borders of the 

 sea, some scattered remains of the products of the adjacent shores, — the 

 plants and animals of the land, with some admixture of freshwater shells. 



(167.) Wealden in other Districts. — The following are the places beyond 

 the limits of the tract described in the preceding pages, in which the presence 

 of the Wealden strata has hitherto been ascertained, or rendered probable. 



Scotland. — In the Isle of Skye Professor Sedgwick and Mr. Murchison discovered, in cliffs 

 of blue shale associated with trap, on the eastern shore of Loch Staffen, flattened masses of 

 limestone, containing several species of shells ; some of which are identical with fossils which 

 I had found in the upper beds of the Weald-clay at Swanage Bay on the Dorsetshire coast; 

 and all the rest are freshwater species belonging to genera found in the Wealden of the south*. 

 The coincident species are the following ; some of which are figured in the plates subjoined to 

 these pages : — Cyclas media (Plate XXI. fig. 10.); Cyclas, a larger species (C. major, PI. XXI. 

 fig. 13., Isle of Wight); Cyclas obovata'i ; Neritina Fttton'i, Mantell (PI. XXI. fig. 7.) ; Ostrea 

 distorta, found with Cyclades in the Isle of Wight, (PI. XXII. fig. 2.) ; Paludina elongata ; Isle 

 of Wight and Swanage Bay ; a transversely elongated Bivalve, (Isle of Wight); an Unto, or 

 Anodon. 



There can be little doubt, therefore, as Mr. Murchison has inferred, that this deposit was con- 

 temporaneous with the English Wealden. 



Continent of Europe. — The places out of England, where the equivalents of the Wealden beds 

 have hitherto been found, are the two following. 



1 . In the Lower Boulonnois the presence of the lower member of the group, at least, is certain ; 

 the strata being almost identical with some of those upon the confines of the Purbeck and Port- 

 land formations in Dorsetshire and the Vale of Wardour. Having given an account of that part of 

 the French coast on another occasion f , it will be sufR.-'ient to mention here, that the line of the cliffs 

 from Equihen on the south of Boulogne to Cape Gris-nez on the north of that place, is capped at 

 intervals with a thin crust of the Purbeck strata, resting upon those of Portland, and consisting 

 of slaty beds of limestone, which contain freshwater shells, and include a bed of tough dark-co- 

 loured clay, in which are numerous fragments of silicified coniferous trunks not distinguishable 

 from those of the Isle of Portland. It is highly probable that a more exact examination of this 

 part of the series, in the cliffs near Boulogne, may lead to the detection of these trunks in the 

 upright position ; and of the Cycadeae by which they are accompanied on the Dorsetshire coast. 



2. The Pays de Bray, near Beauvais, is a narrow tract on the line from Dieppe to Beauvais, 

 extending in length, from the north-west of Neufchatel to the south of the latter city, a distance 

 of about thirtyEnglish miles, and in breadth, at the widest part near the middle, about eight English 

 miles. (See the annexed Map, Plate IX.) It is an opening, or valley of elevation, in the chalk, 



* " Supplementary Remarks", &c., (1827,) Geol. Trans., 2nd Series, vol. ii. pp. 352 and 366. 

 t In a paper including some account of the Lower Boulonnis: See the abstract; Geol. Soc. 

 Proceedings, Dec. 1826, vol. i. p. 9. 



