Notices of Memoirs — G, W. Lamplugh — L. Cretaceous Beds. 551 



175 feet. This drainage would then escape by a narrow notch 

 between Adwick-on-Dearne and Swinton into the Don at Mex- 

 borough. 



A further advance would bring the Wombwell-Swinton valleys 

 into use as overflows, and the Hooton Roberts valley would be the 

 route into the Don. The damming of the Dearne at Barnsley by 

 a lobe of ice would bring into use a couple of small valleys at 

 Barnsley as overflow channels. The gradual advance of the ice 

 across the Conisborough gorge would cause the blocking of the Don, 

 with the formation of a constantly enlarging lake, which would 

 overflow first by the Hooton Roberts valley (180 feet), and then 

 by a series of cuts through the 275-foot contour on Conisborough 

 Parks, first draining into the Don behind Castle Hill, then, as the 

 Warms worth watershed was reached by the ice, into the Balby 

 valley, and, when this was closed by the ice, over the low watershed 

 into the Loversall valley. 



The further advance of the ice-front to Edlington caused a shallow 

 cut to be made through the 300-foot contour, discharging into the 

 Loversall valley and thence into the Trent. This channel, which 

 bends round in a semicircle, became the permanent course of the 

 Wadsworth drainage on the retreat of the ice, the old channel at 

 Balby having been filled up with till. When the ice rose above the 

 330-foot contour the gorge of the Don was entirely closed, and the 

 drainage of the great lake, reaching from Bretton Park and Caw- 

 thorne, north of Barnsley, to Clay Cross and Heath, south of 

 Chesterfield, would all be discharged by the Kiveton gorge into the 

 river Ryton. 



This explanation may be thought to rest too largely on suggestions, 

 but where the evidence is so scattered and imperfect it is difficult to 

 see how this can be avoided if any explanation is to be attempted. 



isroTiCES o:f nvciEn^oiiE^s, ietc. 



I. — Note on Lower Cretaceous Phosphatic-beds and their 

 Fauna. By G. W. Lamplugh, F.G.S.^ 



IT has been customary to regard the fossils more or less imperfectly 

 preserved in the condition of phosphatic casts in different parts 

 of the English Lower Cretaceous series as derivative from the 

 Jurassic rocks. In previous papers the writer has brought forward 

 evidence to show that the fauna of such beds at Speeton and in 

 Lincolnshire is not derivative, but occurs at its proper horizon and, 

 so far as it goes, indicates the life of the period. Personal investi- 

 gation of the localities, and of the fossils obtained from the 

 ' coprolite-beds ' at Upware, Potton, and Brickhill, has led him to 

 conclude that in these deposits also the greater part of the so-called 

 derivatives are really of Lower Cretaceous age. Thus, one of the 



1 Abstract of paper read before the British Association, Cambridge, Section G 

 (Geology), August, 1904. 



