1861.] 



FISHER BRACKLESHAM BEDS. 



87 



It has been seen, in the lists of fossils from the Alum Bay beds, 

 that the Nummul'ma Prestivichiana bed contains Barton forms, viz. 

 Pleurotoma turbida, P. conoides, and Cassidaria amhigua, while the 

 superior beds at that place afford assemblages of fossils exactly 

 analogous to the well-known High Cliff and Barton types. I have 

 therefore assumed the Nummulina Prestwichiana bed at Alum Bay 

 to belong to the Barton series. 



Yig, 2. — Section of High Cliff and Barton Cliff. Length 2 miles. 



1. White siliceous sand. 



2. Band of flint-pebbles. 



3. Sands, with a band of iron- 



stone septaria. 



4. Pebble-bed and fossils. 



5. Dark-green sandy clay. 



6. Slightly indurated marly clay. 

 Brackle- 7. Nummulina Prestwichiana bed. 



sham beds. 8. Grey clays. 



9. " High Cliff Sands." 

 10. " Barton Clays." 



Barton 



I find a bed containing Nummulina Prestwichiana, at High Cliff, 

 analogous to that at Alum Bay. I believe it has hitherto been over- 

 looked, but it may easily be recognized by the following indication : 

 — There will be observed extending along all the central portion of 

 High Cliff, not far overhead, as you walk upon the beach, a narrow 

 band of hard marly clay *, not quite a foot thick, weathering of a 

 reddish foxy tint, and projecting slightly beyond the general face of 

 the cHff. Immediately above this, in marked contrast of colour, is 

 a narrow green band of coarse sandy clay, about 8 in. thick. This 

 is \h.e Nummulina Prestivichiana bed. It is much thinner than at Alum 

 Bay, and the Nummulites are less profusely scattered in it. At this 

 place they are pyritized. They are entirely distinct in appearance 

 from the N variolaria of the sands in the beds above. Now, here 

 this bed is thin, and poor in fossils ; but, judging from the equi- 

 valent bed at Alum Bay, it belongs to the Barton series ; and I have 

 seen nothing above it which would lead me to place it otherwise. 

 I therefore commence my High Cliff section with this bed, as has 

 been done already in the Alum Bay section t. 



* This is the band of tabular soft septaria, mixed with green sand, of Mr. 

 Prestwich's section (Quart. Journ. Greol. See. vol. v. p. 44). 



t The upper part of this section was made more to the east than Mr. Prest- 

 wich's, as may be seen by tlie position of the flint gravel which caps his section. 

 The sliglit differences in the measurements are thus accounted for. It is also 

 carried rather further down. The lower part is often obscured by talus, but 

 was better exposed than usual when I last saw it. 



The fossils of this locality, having lost all their shelly matter, are the less easy 

 of determination. On that account the Lists here given must not be looked upon 

 as beyond question. Nevertheless the characters of the species are better pre- 

 served than in ordinary casts. 



