256 B. Hobson — A Bkplaced Mass of Chalk. 



bodies might be compared to Eadiolaria, but as tbey are now not 

 sharply delimited from the clear matrix, but by a granular structure 

 without other features, it would be rash to assert, save upon further 

 evidence, that they belong to these organisms. In slide D there are 

 some well-defined circular bodies, -03 to -1 mm. in diameter, with 

 clear solid walls, and not infrequently a central spot in each, which 

 very much resemble transverse sections of sponge spicules, and it is 

 possible that this may be their true nature, but some doubt rests on 

 this owing to the apparent absence in the slide of longitudinal 

 sections of spicules. 



Though these fragments give fair evidence of a probably organic 

 origin of the chert, it would need carefully chosen specimens of the 

 rock to furnish proof of the nature of the organisms in it. 



IV. — On a Displaced Mass of Chalk on the Foreshore of 

 Speeton Cliffs, Flamborough Head. 



ByB. Hobson, M.Sc, F.G.S. 



WHEN revisiting Speeton on the 6th of April, 1905, I was 

 surprised to find that the exposures of Eed (Hunstanton) 

 Chalk on the beach at the locality (about 500 yards east of the 

 mouth of Speeton Beck) where the excellent vertical section de- 

 scribed by Mr. W. Hill ^ occurs were almost invisible owing to 

 the accumulation of boulders of white chalk by which they were 

 covered. At length I found a small exposure of Red Chalk near 

 low water mark and, within 3 or 4 yards to north of it, that is, 

 seawards, I came across a reef of chalk in well-defined beds, each 

 perhaps 6 or 8 inches thick, weathered to a brownish or drab tint. 

 This chalk, when freshly fractured, was hard and white, quite unlike 

 the true Red Chalk, although practically at the same level. The 

 prevailing dip of the white chalk of the reef was from 25° to 28° 

 to W. 40° S. mg. (= W. 57° S. true), and the length of the exposure 

 along the strike, so far as the limited time at my disposal would 

 allow me to observe, was %5 paces (say 55 yards), the width in 

 the direction of dip being 16 paces (say 13i yards). So far as 

 I have been able to gather, this reef of white chalk to seaward of, and 

 apjmrently dipping beneath, the Eed Chalk has not been described. 

 Four possible explanations of its occurrence may be suggested. 



(1) It might be regarded as underlying or forming the base of 

 the Red Chalk. Against this view, the totally different character 

 of the white chalk of the reef from that of the true Red Chalk, and 

 the well-known fact described by Meyer ' and Lamplugh ^ that the 

 Red Chalk directly overlies Speeton Clay, are conclusive evidence. 



1 W. Hill, " Ou the Lower Beds of the Upper Cretaceous Series iu Lincolnshire 

 and Yorkshire" : Quart. Journ. Geol. Soc, vol. xliv (1888), pp. 337 and 345. 



2 C. J. A. Meyer, "Note on the Passasye of the Red Chalk of Speeton into an 

 underlj-ing Clay-bed" : Geol. Mag., Vol.'^YI (1869), p. 13. 



' G. "W. Lampluo-h, " On the Subdivisions of the Speeton Clay" : Quart. Jouru> 

 Geol. Soc, vol. xlv"(1889), pp. 581, 603, and fig. 8 facing p. 618. 



