94 Mr. Lyell on a recent Formation of 



shews the exact correspondence between its internal structure and that of the 

 stems of many recent Chara;. (PI. XIII. dg. 6.) 



C. tuherculata (fossil). — This beautiful species of gyrogonite (PI. XIII. 

 fig-. 7, 8.) differs from any yet described in having the valves ornamented by a 

 row of obtuse tubercles^ very regularly disposed. I found it very abundant in 

 a compact siliceous limestone, belonging to the lower freshwater formation 

 between Bembridge and Culver CUff in the Isle of Wight*. The outer inte- 

 gument alone occurs, the nut being always wanting. Its shape is almost sphe- 

 rical ; the spiral valves form constantly nine rings. 



* This new species of gyrogonite was found in White-cliff Bay, close to the point of junction 

 between the horizontal strata of the upper marine and lower freshwater formations, and the ver- 

 tical beds of the London and Plastic clays. This junction is represented by Mr. Webster in 

 Plates XV. and XVII. of Sir H. Englefield's Isle of Wight. 



As I believe no account has yet been published of the strata at this point, the following brief 

 notes, which were made when I collected the specimens, may not be unacceptable. 



Strata, beginning from the top. 



1. Diluvium, sand, gravel, «&c. 



2. Clay of the upper marine formation with numerous oysters. 



3. White calcareous marl, compact, with earthy fracture, having a slightly argillaceous smell. In 



this I observed no organic remains. 



4. Gray calcareous marl, compact, with earthy fracture, filled with the casts of numerous uni- 



valves, which have in general left the hollows which they occupied, empty. They are of 

 the genera Planorbis, Lymnea, Helix, and Paludiua. Gyrogonites also occur chiefly of 

 C, tuberculala ; but I have found one of C. Medicaginula. 



5. White calcareous marl, like No. 3. 



6. A very compact gray limestone, with coiichoidal fracture, containing numerous casts of Lym- 



nea and Planorbis. The gyrogonites in it are very numerous, all belonging to C. tuher- 

 culata. They are replaced by crystals of carbonate of lime. The nut is never within, the 

 integument alone remaining. 



7. Calcareous marl, somewhat resembling No. 3, but grayer, inclosing a few casts of Planorbis, 



small black shining fragments, and a few minute pieces of bone. 



8. White calcareous marl, resembling Nos. 3 and 5. 



9. Compact limestone, fracture conchoidal, contains gyrogonites (C ^M6ercM/a^«) in the same 



crystallized state as in No. 6. 



10. White calcareous marl, like Nos. 3, 5, and 8. 



11. Friable calcareo-argillaceous marl, containing a few Planorbes of which the shells remain. It 



is mottled with oxide of iron. This bed is washed by the sea and covered at high water. 

 Each of the above freshwater strata, from No. 3 to 11 inclusive, are very nearly of the same 

 thickness, varying from 3 to 4 feet each. They have a slight northerly dip. 



