A. Bell— Succession of the Later Tertiaries in Gt. Britain. 69 



included, are found in their living position. It may be also worth 

 noting that the Leda myalls does not occur in the inland Bure Valley 

 Beds or the Weybourne Crags, where L. oblong oides (L. Umatula) is the 

 representative species, and of the 18 Bure Valley marine species, 

 eight do not occur in the Myalis Bed ; and of the 15 species in the 

 latter, nine are not found in the Bure Valley. 



I may call Mr. Beid's attention to a very valuable paper by Dr. 

 Nathorst, on this Arctic plant-bed, in vol. iii. of the Journal 

 of Botany, London, which Mr. Beid seems to have overlooked (op. cit. 

 p. 83), in which the Doctor records the species he obtained, including 

 a large number of Willows and Mosses now living only within the 

 Arctic circle. 



It is generally assumed that a great elevation of the land was 

 taking place throughout the earlier part of the major glaciation, 

 culminating in a rise to at least the 100-fathom line, raising the 

 whole bed of the North Sea, except a narrow valley towards the 

 Norway coast — the ice-sheet then generated not extending to the 

 South of Britain. Of the land or sea life of this period there is no 

 record in Britain, but it may be surmised that the Mammoth and 

 Rhinoceros tichorhinus, the Wolverine and the Musk Sheep roamed the 

 frozen solitudes in scanty numbers. That which would be most con- 

 sonant with the climate is found in the masses transported bodily from 

 some unknown deep-sea locality, imbedded in the higher Yorkshire 

 Clays at Bridlington and elsewhere (vide infra), the few fragments 

 mentioned by Mr. Beid from the Cromer Drift being doubtfully 

 in situ. 



Subsidence of the land is indicated by the erosion prior to the 

 deposition of the wide-spread sheets of Middle Glacial sand and 

 gravel extending from Shropshire to Belgium (if, as Mr. S. V. Wood 

 suggested, the Sables de Campine are of this age). These sands are 

 mainly, and I am inclined to think altogether, unfossiliferous. The 

 very fragmentary condition of the large number of species (94) 

 recorded by Mr. Wood from these sands, and the fact that except 

 six or seven all are present in the Butley Crag, induce me to think, 

 contrary to the opinion of the Messrs. Wood and Harmer, that, like 

 the corresponding sands of Slains and Cruden, containing frag- 

 mentary Bed Crag shells, they are purely derivative. 1 It is also 

 difficult to see where such a fauna could have existed in continuity 

 throughout the preceding stages, if the bed of the North Sea had 

 been elevated to the extent supposed. These sands and gravels are 

 apparently due to the floods let loose by the melting ice, excessive 

 rainfall, and the sorting action of the sea as a greater area was 

 brought under its infhience while the land slowly subsided. The 

 immense influx of freshwater would be unfavourable to the develop- 

 ment of marine life which in the Anglo-Belgian Gulf had ceased to 

 exist, the incoming northern fauna being unmodified by southern 

 accretions till the future minor glaciation had passed away, and the 

 communication re-opened between the Channel and the North Sea. 



1 Traces of Red Crag Shells, Pecten opercularis, have also been found in the 

 westerly extension of the Middle Glacial. 



