290 Mr. Lyell on the Freshwater Strata of Hordwell Cliff, 



e. Light bluish gray marl with vegetable impressions, 1 foot. 

 /. Black carbonaceous clay and lignite, 6 inches. 

 g. Green clay, 1 foot. Total thickness of No. 8. about 9 feet. 

 9. White siliceous sand, without shells, rises near Long-Mead-End and extends through Beacon 

 and Barton Cliffs to the middle of Ilighcliff. 



Besides the organic remains above enumerated^ scales of tortoises have been 

 found by some collectors*. They occurred either in the group of strata 

 No. S, or in that termed No. 4_, of the above section. Gyrogonites also have 

 been found in abundance in the same part of the cliff, though I did not ob- 

 serve them myself. In No. 3, the seed-vessel called by M. Brongniart car- 

 polithes thalictroides-f has been procured. In No. 4_, teeth of a crocodile or 

 some saurian animal^ and lozenge-shaped scales offish? 



On reviewing the strata described in the above section, and their contents, 

 the following observations occur. 



1st. No portion of the upper marine formation exists anywhere in this part 

 of the Hampshire coast. The uppermost beds of the series in Hordwell Cliff, 

 so far from indicating a passage into the upper marine formation, contain or- 

 ganic remains, both animal and vegetable, exclusively belonging to freshwater 

 genera. The shells referred to by Mr. Webster as cerithia, occurring in 

 fallen blocks along the shore, belong to the genus Potamides of Brongniart, 

 and the stratum in which they abound occupies a middle place in the series. 

 Cerithium is a marine genus; but the potamides, of which some species still 

 exist in a recent state, inhabit rivers, or at least the mouths of rivers J. 



2ndly. The extent of the freshwater formation is somewhat greater than had 

 been supposed, as it is continued in Barton Cliff to nearly opposite the village 

 of Barton. The lower beds of the series there exposed contain in parts gyro- 

 gonites and freshwater shells. 



Srdly. The fine white siliceous sand of Beacon and Barton Cliffs must, till 

 some reason be shown to the contrary, be referred to the freshwater forma- 

 tion : for it will be seen by the above description, that two beds of a similar 

 fine white sand occur associated with the freshwater strata in Hordwell Cliff'. 

 It is therefore clear, that when this series was deposited, all the circumstances 

 existed which were required for the formation of such sand ; whereas nothing 

 similar is found connected with the London clay in any part of England. The 

 lower freshwater formation must thus be considered as extending throu"hout 

 Barton Cliff to about the middle of High Cliff. 



* The entire shell and bones of a tortoise have lately been found in the lower freshwater for- 

 mation near Thorness Bay, in the Isle of Wight, 

 t Cuv. Oss. Foss. torn. ii. edit. 2de. PI. XL f. 5. 

 J Cuv. Regne Anim. torn. ii. p. 438. 



