T1IK CKKTACEOUS SYSTEM 483 



Tnriii.it, !i. i Mcn.ir.li. Raphidonema faringdonensis. 



,, Fittoni. I iriitatocystia anastomosans. 



Rhynchonella latissiiua. Peronidella ramosa. 



The summit of Shotover Hill, south-east of Oxford, consists of 

 ferruginous sands with bands of ochre and cream-coloured loain, 

 which contain remains of freshwater shells, Unio, Cyrena, and 

 I'/riparus. Similar beds occur at Wheatley, Brill, Crendon, and 

 Tli.une, where they include beds of grey and lilac clay. At Crendon, 

 Pecten aptiensis has been found in a layer of calcareous concretions 

 which overlies the clays, and marine fossils have also been found 

 at Stone near Aylesbury. Hence there can be little doubt that the 

 Shotover Beds, which rest in some places on Portland, in others 

 on the Purbeck Beds, are freshwater deposits of Aptian age. Their 

 thickness is variable with a maximum of about 50 feet. 7 



Yellow and white sands emerge from beneath the Gault near 

 Leighton Buzzard and form a range of hills by Woburn and 

 Ampthill as far as the neighbourhood of Shefford. Near their 

 base are beds of phosphatic nodules, which were worked near 

 Brickhill, and include casts of fossils derived from the under- 

 lying Jurassic Clays, together with well-preserved contemporaneous 

 fossils. Among the latter are Terebratula sella, T. depressa, T. 

 microtrema, T. moutoniana, and others, Terebratella Menardi, T. 

 Fittoni, Waldheimia celtica, IV. tamarindus, and others, Peltastes 

 IVrighti, and many of the Faringdon sponges. 8 



The sands above are dug for glass-making purposes, and are 

 believed to be about 200 feet thick near Woburn ; they also 

 contain a band of Fuller's Earth, which has been worked for more 

 than a century. 



These Woburn sands, passing beneath the valley of the Ivel, 

 become conspicuous again near Sandy and Potton, with the same 

 nodule beds near the base, in which derived reptilian bones are 

 very abundant ; thence the sands run through Cambridgeshire 

 to the Fens south of Ely, near Streatham and Upware. 



At Upware in the Fens of Cambridgeshire are sands and silts 

 with two nodule beds similar to those of Brickhill and Potton, 

 but containing a still larger number and variety of fossils. The 

 beds are banked against the Corallian limestones, are less than 

 12 feet thick, and are overlain by the Gault, so that they seem 

 on the point of thinning out. 



3. Northern District 



This includes the Lower Cretaceous tracts in the counties of 

 Norfolk, Lincoln, and York. Each of these exhibits a somewhat 



