xx SUPPLEMENT TO THE CRAG MOLLUSCA. 



In tracing this drift from the East coast at Hopton, and from the numerous inland 

 sections of the extreme North of Suffolk and East of Norfolk, towards the Cromer coast, we 

 see it in a fine section at West Somerton, overlain by the sand, No. 8, which is again close 

 at hand overlain by the clay, No. 9 (see Section M), and we then lose it by the interven- 

 tion of several miles of marsh. On the cliff beginning to rise at Eccles the drift appears 

 again in the identical form of reddish-brown brick-earth possessed by it at Somerton, but 

 overlain by a thin bed of stony clay (No. XI), to be presently noticed. Erom this place 

 westwards it can be seen to assume gradually the finely stratified appearance it possesses 

 at Hasboro', and then to change still further west into its original red Brick-earth 

 condition. 



This deposit must once have spread far to the southward, for what appear to be 

 outliers of it occur at Kesgrave (five miles south-west of Woodbridge), and at Blaxhall, 

 half a mile east-north-east of the church (seven miles north-east of Woodbridge) ; while 

 beyond the limits of the map we have found it in the south-west of Suffolk, near 

 Boxford, and probably at Sudbury. The Blaxhall outlier contains marl masses similar 

 to those in the North Norfolk coast section. 



The breaking off of this deposit into outliers southward is evidently due to a great 

 denudation of the Lower Glacial formation prior to the accumulation of the Middle 

 Glacial sands, which occupy to a great extent troughs or valleys in the Lower 

 Glacial beds ; and it is quite possible that outliers of it may be concealed under the 

 tablelands of Middle Glacial sand which separate the East Anglian valleys from each 

 other in Section A. It is clear that the valley system of East Anglia had its inception in 

 this denudation, though it would be beyond the scope of the present outline to show this 

 further than appears from the sections accompanying the map. 1 



The Contorted Drift has yielded no fauna as yet worth mentioning ; but Tellina 

 Balthica and fragments of Cardium edule, Cyprina islandica, and Mactra ovalis, and of a 

 Mya, are not unfrequent in it. We took from it at Elsing (twelve miles west-north-west 

 of Norwich) the femur of a small mammal. 



The Middle Glacial (No. 8). 



This formation is principally composed of sand within the limits of the map, though 

 gravel is more or less intermixed in places ; but southwards, towards and over Essex, the 

 formation consists mainly of gravel. These sands have their greatest thickness over the 

 Red Crag region, and were long confounded with that formation, under the term " un- 

 productive sands of the Crag." Although the sands over the Crag are treated by us as all 



1 We should explain, however, that it is to this intraglacial erosion that the chalky clay (No. 9) owes 

 its abnormal position in the bottoms of valleys cut through the older Glacial beds — a position which, before 

 we had discovered the true explanation of it, led us to suppose (as suggested in vol. xxiii of the ' Quarterly 

 Journal of the Geological Society,' p. 89) that the clay in the valley bottoms was a different Boulder clay of 

 subsequent origin to the clay No. 9. 



