TIIK I'l.locKNK SK1I1KS 





!.> idedly i.l. In- than lliat in the northern part. The beds at 

 WaltOH-OH-NaM yield a fauna that Mr. Harnu-r con.-iders to be 

 closely allied to that of the Coralline Crag, for it includes many 

 soiitln-rn BpeOM ami very few of northern origin, while at Butley 

 in the northern ]>art of the area northern >]iede- are abundant and 

 southern forms are comparatively rare. Thus it seems as if these 

 Red Crags wen- deposited while the sea was gradually retreating 

 northwudfl, the slowly receding waters leaving a succession of 

 beach and shallow-water deposits behind them. This shelly crag 

 i* -eldom more than 20 feet deep at any one place, and its bedding 

 is generally oblique, so that it may te described as consisting of a 

 number of shelly sand-banks, each composed of highly inclined 

 laminae, one bank often being sharply truncated by another. 



Mr. Manner lias recently divided the Red Crag into three parts 

 on the basis of the changing proportion of northern and southern 

 species, and these divisions may be termed the Walton Crag, the 

 Newbourn Crag, and the Butley Crag. The relations of these 

 crags is best expressed by the following table of percentages, in 

 the compilation of which Mr. Harmer has taken into account only 

 the more abundant and characteristic species. 



The Walton Crag is characterised by the abundance of Neptunea 

 contraina, Columbella sulcata, Nassa labiosa, N. elegans, Trochus 

 Adansoni, Buccinopsis Dalei, and Dosinia exoleta ; the New- 

 bourn Crag by abundance of Cardium angustatum, Mactra ovalis, 

 M. constricta, and Tellina obliqua ; the Butley Crag by Neptunea 

 i in tii/ a a, Buccinum grcenlandicum, Cardium grcenlandicum, Nucula 

 Cobboldice, Tellina obliqua, and T. pnetenuis. 



Norwich Cragf. This group has a more extended range than 

 either of the older rnigs, since it is found more or less continuously 

 through Eastern Suffolk from Aldeburgh to Bungay and Beccles, 

 and thence through Norfolk to Brundall and Norwich (on the 

 river Yare), and to Coltishall and Burgh in the Bure Valley, a 

 distance of about 40 miles. It is well exposed at several localities 

 in the neighbourhood of Norwich, whence it takes its name ; it is 

 a variable group of sands, laminated clays, and pebbly gravels, 



