492 ME. M. ODLING ON THE [Oct. I9I3,. 



(b) Blackthorn Hill, south-east of Bicester. 



This section is largely based on the evidence obtained by the 

 officers of H.M. Geological Survey, and by the Geologists' Association,, 

 since the exposure was earthed up before this investigation had 

 been begun. There was a clay-pit near here, which has been 

 described by A. H. Green. 1 I had, however, previously visited 

 the section in company with Prof. Sollas in May 1908, while the- 

 excavation was in progress. 



The Cornbrash is very thin, being only 5 feet 3 inches thick, and 

 is covered by what may possibly be the Kellaways. 2 In the cutting 

 the following section is recorded by the Survey 3 : — 



Thickness in feet inches^ 

 Cornbrash. (Lower part only. Bubbly, sbelly, non-oolitic lime- 

 stone) 5 



( Sandy clay, with one pale marl- band 3 6 



■ j Hard, grey, oolitic limestone 1 6 



Dai-k tenacious clay, passing clown to lighter clay, 



i with three pale marl-bands 7 



Forest J Pale-grey blotchy limestone 3 6 



Marble, j Pale clay-parting 6 



Hard clay-limestone 1 9 



Pale-grey clay 6 



Bright bluish-green clay, passing down into grey clay 



with (?) phosphatic noclules 3 6 



At the time of my visit, only the lower beds of the Cornbrash 

 were exposed. They yielded the following fossils: — 



Psendomonotis echinata (Sow.). i Pholadomya deltoidea Sow. 



Pleuromya securiformis Phil. i Pecten vagans Sow. 



Terebratula intermedia Sow. | Omithella obovata (Sow.). 



Near the top of the Forest Marble a greyish marly band contains 

 numerous specimens of Gervillia cf. waltoni Lye. The basal bed 

 evidently corresponds with the basal clay in the Ardley section ; 

 while the Forest Marble is, as a whole, more calcareous, and con- 

 tains more wood than in that section. At Blackthorn Hill the 

 whole of Block 1 of the Great Oolite was exposed, and about 

 18 inches of Block 2, the sequence being the same as in the Ardley 

 section. 



(c) Islip Sections. 

 One quarry, now no longer worked and much overgrown, is seen 

 on the right-hand side of the road leading from the village to the 

 mill. The section shows about 4 feet of Cornbrash resting upon 

 the Forest Marble, which consists of about 4 to 6 feet of clay 

 overlying false-bedded rock: the lower 6 to 8 feet is hidden by 

 talus, and so overgrown that the thickness of the rock cannot be 

 ascertained. A band of clay occurs at the very base of the quarry, 



1 ' Geology of the Country round Banbury, &c.' Mem. Geol. Surv. 1864, 

 pp. 36-37. 



2 H. B. Woodward, 'Jurassic Rocks of Britain' Mem. Geol. Surv. vol. iv 

 (1894) p. 449. 



3 G. Barrow, Proc. Geol. Assoc, vol. xxi (1909-10) p. 37 ; and ' Summary of 

 Progress of the Geological Survey for 1907' Mem. Geol. Surv. 1908, p. 145. 



