IRON SAND FORMATION. 33 



consecutive deposits. The limestone of Framfield, like that of Ashburn- 

 ham, Kotherfield, &c. is almost wholly composed of a species of Tellina * ; 

 it is exposed to view on the side of the road leading from Lewes to the 

 Black-boys, nearly opposite to the ninth mile-stone, and is only occasionally 

 quarried. 



It lies but a few feet beneath the surface, and occurs in horizontal 

 strata, divided into thin slabs by layers of blue clay, that contain laminae 

 of a reddish brown shale, and shells of the same kind as the limestone. 

 In the section (fig. 2. tab. III.) these beds are represented as if lying in 

 a basin or hollow of the iron sand ; but subsequent observations have 

 convinced me that this position is incorrect, and that the limestone forms 

 an intervening deposit. 



At Isfield, about six miles from Lewes, in sinking the well near the 

 Paper Mill, a layer of bivalve hmestone was discovered in a bed of blue 

 clay at the depth of ninety feet. It evidently belongs to the same 

 deposit as that of Framfield, but the shells appear to be of a different 

 species; Mr. Wood (author of General Conchology, &c.) considers them 

 as nearly related to Tellina cornea, if, indeed, they are not of the same 

 species. 



The geological position of these argillaceous limestone strata is in- 

 volved in some obscurity. The lowermost beds at Ashburnham are 

 supposed by an eminent geologist f, to coincide with those of the Pur- 

 beck hmestone ; but at the same time he remarks, " that until they shall 

 have been more scientifically observed, it is impossible to speak with 

 absolute certainty." In the present imperfect state of our knowledge, it 

 may indeed be disputed, whether these beds alternate with the ferruginous 

 sand, (as represented in fig. 3, tab. III.) are situate in a hollow or basin 



* Mr. G. B. Sowerby, author of " The Genera of Recent and Fossil Shells," kindly 

 obliged me by an examination of the shells contained in the Framfield limestone. The general 

 appearance of some of the specimens he thought resembled the Nuculce, but other circumstances 

 led him to consider it probable that they might belong to the genus Cyrene ; the important 

 question whether they are of marine, or of fresh water origin, is therefore still undecided. 



-f- Rev. W. Conybeare, in Phillips' Geological Outlines, &c. 



