Dr. FiTTON on the Strata below the Chalk. 275 



" so abundant as to concrete the sand into shapeless masses of great hardness, which occur in 

 " local strata a few inches tliick. Except in these masses of ironstone, no organic remains have 

 " been noticed throughout tlie deposit. Taken as a whole, this formation bears a great resem- 

 " blance to the Lower green-sand of Sussex ; and tiie masses of ironstone are almost identical in 

 " appearance with some which exist there : but the fossil shells lately found in it appear rather 

 " to show that it forms a part of tlie Wealden group. These shells occur only in the nodular 

 " masses of ironstone, which are scattered near the old sand-pits on the west end of the hill ; and 

 •' were first noticed there by the Rev. H. Jolly of Bath." 



[The shells here referred to by Mr. Strickland, appear to belong to five species : three of 

 Paludina; a small bivalve, like a Cyclas ; and a larger bivalve, like a Unio. But the specimens 

 hitherto found are all too imperfect to admit of precise determination, and are none of them so 

 unlike some of the species which occur in the Lower green-sand, as absolutely to exclude them 

 from that formation.] 



" A small pit had been sunk in quest of ochre at the side of the old London road, about 150 

 " yards to the east of the old quarry, where the large globular concretions of the Portland sand 

 " occur. This spot may be about 50 feet above that quarry ; and the pit presented the following 

 " Section : — 



[^Wealden'!'] Ft. In. 



" 1. Yellowish clay 4 8 



" 2. Yellow ochre 4 



" 3. Sand and rubbly marl 3 



[^Portland.l 



" i: Very hard brown sandstone, with a few Trigoniae, and a bone of a crocodile 1 



" 5. Rubbly stone, with numerous casts of Trigonia, the shells having decayed into al , . 

 " brown powder J 



" Total 10 



" The first three beds exactly resemble the sandy strata which extend from this point to the top 

 " of the hill, a height of about 50 feet, and which I am disposed to regard as belonging to the 

 " Wealden group. The nodules of ironstone containing the supposed freshwater shells, occur at a 

 " height of about 30 feet above No. 4." 



Purbeck Strata.- — What remains of the Purbeck strata in this part of the country is best seen 

 in the pits in the southern part of the Shotover range, at Combe Wood and Garsington. The 

 junction of the incumbent strata with the Portland beds, is first disclosed in the quarries at Great 

 Hazeley. 



The section at Combe Wood consists of, — 



1. Reddish loamy soil, passing into 2. 



2. Ferruginous sand {Lmver green). 



8. A thin bed of very tough clay (Fuller's earth?); which, with 2, enters into, and follows the 

 deep erosions and irregularities at the top of 4. 



4. Purbeck. — Stone, and soft rubbly matter ; — (the "Malm" of the pits at Garsington) ; containing 

 freshwater shells, like those of that place: — Cypris; Mytilus, two species; Modiola; Paludina 

 elongata, and perhaps another species? ; Planorbis-?. Some portions of the stone are compact 

 and uniform, with the usual characters of freshwater limestone ; others, though containing the 

 same fossils, are composed of grey and brownish, fine-grained, oolite, in which a very small 



