SECTIONAL TRANSACTIONS.— 0. 323 



Dr. S. W. Wooldridge. — The Denudation Chronology of South-east 

 England. 



This paper attempts to evaluate and to arrange in order of date the several episodes 

 of planation legible in the land-forms of S.E. England (Weald and London Basin). 

 Brief reference is made to the earlier episodes, more particularly the Miocene 

 sub-aerial planation whose work was completed by the Lenhamian sea. The several 

 stages of the post-Lenhamian rejuvenation of the river-system is traced and em- 

 phasis laid upon the widespread occurrence of a dissected plain at 200-250 feet O.D. 

 This feature is traced in the several water-gaps of the northern Weald and in the country 

 lying north and south of them. Its occurrence in the London Basin, north of the 

 Thames, is demonstrated and its relation to the glacial deposits discussed. From this 

 and other evidence indications of age are obtained and it is interpreted as a base-level 

 of late Pliocene or early Pleistocene date. Some description is given of the character 

 of the deposits resting on the plain, and attention is drawn to the prevalence of drainage- 

 modifications as evidenced by wind-gaps, on the surface of the plain. The question 

 of wider correlations is broached, though the evidence does not permit of definite 

 conclusions being drawn. Some interest attaches to the regions, notably East Anglia 

 and parts of the southern Weald, where the 200-foot platform cannot be traced and 

 reasons for its absence are suggested. 



The Rev. Dr. S. G. Brade-Birks. — The Bionomics and Affinities of 

 Archipolypoda. 



Scudder (1882) x in his study of Archipolypoda from the Carboniferous rocks of 

 the United States suggested a possible aquatic habitat for Acantherpestes major on 

 the strength of the anatomical features exhibited by the ventral plates. He inter- 

 preted the openings seen on a typical ventral plate as a pair of medioventral branchial 

 cups, a more laterally placed pair of openings for the insertion of the legs and, outside 

 the base of each leg, an oblong-ovate spiracle. Verhoeff (1926) 2 has compared his 

 own interpretation of like structures in Acantherpestes gigas with that of Fritsch 

 (1899). 3 Since Jackson and the Brade-Birkses (1919) 4 gave their account of 

 Palaeosoma gigantevm, a new specimen of Euphoberia ferox from the Northumberland 

 coal measures has become available for study and for comparison with other 

 specimens of the same species elsewhere, and with the specimen oiPalaeosoma giganteum 

 preserved in the Manchester Museum. 



Recent Colobognatha, Thysanura and Symphyla exhibit some structures worthy 

 of comparison with those of the Archipolypoda. This makes a discussion of the 

 bionomics of a number of species possible and helps to throw light upon the origin 

 of the arthropod land fauna. 



The structure and affinities of the genus Kampecaris are considered. 



Prof. P. G. H. Boswell. — The Source of the Constituents of the Lower 

 Greensand and other Aptian Sediments. 



A review of the palaeogeographic features of the British area in Aptian times indicates 

 that the possible land-masses which might have contributed detrital material to the 

 Aptian sediments were (1) the now-buried Palaeozoic floor under the east of England, 

 (2) the south-western Hercynian massif, (3) the western and north-western Palaeozoic 

 rocks with their fringe of Jurassic and Triassic strata, and (4) smaller masses of ancient 

 rocks partially buried under newer sediments in the Midlands. The peculiar characters 

 of both coarse and fine detrital constituents of the Lower Greensand, as determined 

 by numerous investigators, indicate that no known British sediments can be regarded 

 as their source. Only newly exposed metamorphic rocks (and probably acid igneous 

 rocks) could have yielded the fresh material of the Greensand. Unfortunately, the 

 older Palaeozoic rocks known from deep borings under eastern England are not of a 

 type to satisfy the requirements, nor are those of the west and north-west of England 



1 Mem. Boston (U.S.A.) Soc. Nat. Hist., vol. 3, No. 5, p. 155, &c. 



2 ' Fossile Diplopoden,' in Bronn's Klassen und Ordnungen des Tier-Reiclts, 2. Abt. 

 2. Buch, p. 330, &c. 



3 Fauna der Gaskohle . . . Bohmens. 



4 Geol. Mag., Dec. 6, vol. Q, p. 406, &c. 



Y2 



