part 3] MOLLUSCA FROM THE CAMBRIDGE GRAVELS. 211 



Barrington (upper layers) is certainly later, and has no exact 

 equivalent in the Thames Valley. It is probably later than Cray- 

 ford. 



A still later stage is represented by the .upper layer at the 

 Downing Section ; while the last stage, Barnwell Station, is the 

 equivalent of the Arctic Beds of the Lea Valley. There has been 

 considerable divergence of opinion as to whether these gravels are 

 Preglacial, Interglacial, or Postglacial, and the literature relating 

 to this is voluminous ; but there is no need to enter into the various 

 arguments that have been adduced. 



If the deposits are judged from a palseontological standpoint, 

 there is only one conclusion, and that is that, with the exception 

 of the Barn well-Station beds, they are all Preglacial. It is, indeed, 

 a noteworthy fact that, wherever stratigraphical evidence is avail- 

 able, the Arctic Bed is always above the other Pleistocene deposits. 

 In no case is an Arctic Bed succeeded by deposits of undoubted 

 Pleistocene age indicating genial conditions. Hence it is clear 

 that there has been only one cold period, and this occurred at the 

 close of the Pleistocene. 



Appendix II. 



Notes on the Implements. 

 By Miles Crawford Buekitt, ALA., F.G.S. 



In considering those implements of undoubted human manu- 

 facture that Prof. Marr has discovered at the Traveller's Rest 

 gravel-pit, two more or less distinct series seem to be present: — 



(a) There is a series of much waterworn implements, which are 

 in some cases stained deep ochreous-brown and in other cases 

 greenish bluish-brown. These are undoubtedly of Lower Palaeo- 

 lithic age. Without faunal evidence — that is, alas, completely 

 lacking — it would be difficult to say how much is Acheulean and 

 how much Chellean. At any rate, forms of undoubtedly Lower 

 Palaeolithic age are common. 



There are both large and small coups-de-poing, side scrapers 

 with a Chellean trimming, worked Hakes, etc. Many of these 

 very much recall the industry at 'Three Mills." There are also a 

 number of unworked triangular Hakes that have been struck off 

 by a blow which leases a good bulb of percussion : similar Hakes 

 are found at 'Three Hills.* A rough sort of core-scraper has 

 also been found, which, owing to its deep ochreous-brown patina, 

 would belong to this series. 



There is, too, a small coup-de-poing with the twisted sides that 

 are so typical of the Acheulean period. 



(b) A series has also been found which, on examination, leave.- 

 a totally different impression. Whenever implements of this series 

 have been obtained in situ, they eome Erom upper levels of the pit. 

 The rest (as also those of series a) have been collected from heaps 

 left by the workmen. 



This series is usually bluish and is much less waterworn. No 

 Q. J. G. S. No. 299. l 



