TRANSACTIONS OF SECTION C. 59 1 



tbsa 4 inches thick, and it has been dragged out at both ends into a mei'e thread 

 in the boulder clay. Nevertheless, some of the shells are quite perfect, and the 

 Astartes (by far the commonest forms) frequently occur with valves united. In 

 other cases the valves have been trailed apart by shearing, but remain without 

 fracture; while, still more frequently, the shells have been crushed into fragments 

 and drawn out into a white streak. 



In the previously-known localities the rare exposures of these shelly patches 

 have taken place either in the clifi-foot or on the foreshore, so that, even when 

 visible, it has only been possible to study the upper portion of the deposit which 

 contained them. At the South Sea Landing, however, the shelly bed occurs in a 

 cliif about 100 feet high, which shows the whole of the drifts overlying 30 to 40 

 feet of chalk. In this section stratified beds of sand and gravel are revealed both 

 above and below the boulder clay which contains the shelly patch, but in neither 

 position do these beds show any evidence of a contemporaneous fauna. We thus 

 learn, what was before suspected, that these shell-bearing masses have not been 

 derived from the destruction of beds pre-existing in their immediate vicinity, but 

 are truly transported boulders. 



The section is also valuable as placing beyond doubt the extension of the base- 

 ment boulder clay of Ilolderness over Flamborough Head. 



7. Did the Great Hi vers of Siberia flow Southwards and not Northwards 

 in the Mammoth Age ? By Henry H. Howorth, M.P., F.S.A. 



During the mammoth age the mammalian fauna of the Palse-arctic and Ne- 

 artic regions was very nearly homogeneous. The remains of the mammoth, the 

 bison, the elk, the horse, the red-deer, &c., are indistinguishable, whether found in 

 Northern Asia or in North America. 



This fact makes it clear, as the author has ventured to urge in the ' Geological 

 Magazine,' that at that time there was a land communication between the two 

 areas, and, as he has also attempted to show, this communication must have been 

 across the Arctic area, which in the mammoth period was occupied by dry land, when 

 comparatively mild conditions prevailed. This is also necessitated by the fact of 

 finding numerous remains of the great mammals unweathered, and doubtless where 

 the animals died, in the Liachof Archipelago, the Bear Islands, &c., some of them 

 at least 200 miles from the mainland. 



If the polar area was converted into diy land it would mean the elevation of 

 the floor of the eastern part of the Arctic Sea to the extent of from 25 to 40 

 fathoms only, no greater depth having been met with there in the numerous sound- 

 ings recorded from the time of Belcher to those made by the Jeamiette exf edition. 



The Siberian rivers have notoriously a very slight fall, and, as has been said, 

 there are points where they seem in doubt as to whether they shoidd flow one way 

 or the other. A series of careful levellings has been made by the Russians, and 

 published by Petermann, which shows that a rise of from 25 to 40 fathoms at the 

 mouth of at least two of these rivers — namely, the Yenisei and the Obi — would 

 reverse their drainage, and make them flow southwards instead of northwards. 



If we turn elsewhere we have a continuous chain of facts showing that, in the 

 latest geological age, there was a .Mediterranean Sea in Central Asia, of which the 

 Cas])ian, the Seas of Aral and Balkhash, and the innumerable small lakes scattered 

 over the so-called Kirghis steppes are the dt5bris. The fact that they are what 

 the Germans call Reliktenseen is shown by their fauna, and is generally accepted. 

 Besides these, we have the evidence of great stretches of sand, strewn with marine 

 shells in a semi-fossil condition, which intervene between the lakes. 



These facts have combined to make a former Central Asiatic sea a postulate of 

 elementary geography, but hitherto there has been no theory forthcoming to ex- 

 plain it. The reversal of the Siberian rivers would create and maintain such a sea ; 

 and the evidence is therefore bilateral and very strong that in the mammoth age 

 the drainage of the greater part of Siberia was reversed. 



It is curious that European Russia, which in other respects is a mere continua- 



