﻿404 ME. K. M. BRYDONE OX THE [-^^^g* IpoS^ 



the two sets of beds immediately succeeding. P. globidaHs is very 

 abundant in these lower beds, quite scarce in the three succeeding 

 sets of beds, and has hardly ever been found by me in any of the 

 other beds, in which it must be exceedingly rare. The thickness 

 of the beds («) exposed is probably about 8 feet. 



The beds next above those just described are those designated by 

 me as ' Sponge-Beds ' (c). They are about 12 feet thick, strongly 

 yellow in colour, and more or less hardened, sometimes so much 

 so that a knife makes practically no impression, with the natural 

 result that they always present a rugged surface on the foreshore.. 

 I have taken as their upward limit a greasy-looking and clayey 

 bed, which for the last year or so has thrown out a fairly persistent 

 spring of fresh water at the foot of the Bluff. Below the half-tide 

 level only about half the thickness of the beds is cut through along 

 the crown of the anticline, which is there much flatter than it is 

 near the Bluff. As a result of this flattening, the two uppermost 

 flint-bedSj which both consist of long slender flints with pitted 

 surfaces, occupy a considerable area on the foreshore and form an 

 easily recognizable feature. Thecidium vermiculare appears in these 

 beds. The four-angled variety of Serjnda canteriata appears to be 

 entirely confined to them and to the preceding and succeeding sets. 

 A Nautilus which has been found in them is thought by llr. G. C. 

 Crick to be probably N. BeVeroplion, a Danian form. 



The next set of beds (c?), about 9 feet thick, consist of White- 

 Chalk without 0. luncda. IJntil quite recently they had never been 

 well exposed for study, but a very fair idea of their fossil-contents 

 has now been obtained. Terehratida secc-radiata and the four-angled 

 variety of Serpula canteriata have both been found to persist in the 

 lower part, while Porosphcera glohidaris is not infrequent. Up to 

 this point large specimens of RhyiidioneUa plicatilis have been fairly 

 abundant, but the species now becomes scarce and small. 



The next set of beds, with Ostrea lunata^ is the highest of this^ 

 sequence yet known (e). It is a curious fact that nowhere in the 

 foreshore has any trace been found of the highest line of flint seen 

 in the Bluff", although the one next below it is frequently preserved. 

 This top line of flint is very thick and solid. The strong line of 

 flints seen, the second from the top in the Bluff, is the highest that 

 is regularly preserved on the foreshore, and it forms a well-marked 

 feature wherever it occurs. The double line of flints in yellowed 

 chalk, which forms the base of this set of beds, is even more valuable 

 in tracing them on the foreshore, for Ostrea lunata is so relatively 

 scarce in the lowest bed of this set that it would often (but for this- 

 well-marked line of flints) be impossible to fix the boundary between 

 this and the preceding set of beds without prolonged search. In 

 collecting from below upwards, Terehratida secc-radiata, PorospJuvra 

 nuciformis, and the four-angled variety of Serpula canteriata 

 apparently disappear for good before we reach the lunata-Qhdlk ; 

 and Porosphcera glohidaris disappears long before the top is reached. 

 Ostrea lunata and Crania spinulosa here make their appearance, and 

 Thecidium verraicidare becomes fairly common. These beds are at 

 least 20 feet thick, and the total thickness of Chalk exposed in the 

 block is estimated as at least 50 feet. 



