462 PLIOCENE. 



The Red Crag is well shown at Walton-on-the Naze, Felixstow, 

 Waldringfield, Sutton, Ramsholt, Trimley, Bawdsey Cliff, Butley, 

 Hollesley, etc. Its presence at Sudbury has been noticed by Mr. 

 Whitaker.^ Near Aldborough, at Sudbourne, and at Park Farm, 

 Tattingstone, near Ipswich, the Red Crag was to be seen in section 

 superimposed upon the Coralline Crag ; the beds are uncon- 

 formable. (See Fig. 77.) Over the greater part of the area the 

 Red Crag rests on the London Clay. 



Fig. 77. — Section North of Aldborough, in Suffolk. 

 (Prof. J. Prestwich.) 



High road, near 

 Warren House. 



Railway 

 Cuttinjj. 



5. White sand and gravel (Glacial Drift). 



4. Chillesford Clay. 



3. Chillesford Sand. 



2. Red Crag. 



I. Coralline Crag. 



Height about 25 feet. 



In 1839 Lyell- described an old cliff of Coralline Crag at Sutton, against which 

 the Red Crag rested, and from which it derived niucli material, and Prof. Prestwich 

 speaks of the Red Crag as occupying "an excavated area in the Coralline Crag, 

 wrapping round the isolated reefs of the latter, filling up the hollows between 

 them, and lying nearly on a level with the conterminous Coralline Crag." ^ Many 

 organic remains found in the Red Crag have been derived from the London Clay 

 and the Coralline Crag ; about 25 species of the Mollusca have, it is thought, been 

 derived from the latter formation. 



The fossils of the Red Crag include the Troplmn i^Fiistis) antiquus, 

 of which the sinistral or left-sided form (var. contrarhis), is found 

 in the Walton Crag, while the dcxtral form abounds in the rest of 

 the Red Crag. Other Mollusca are Pecteji opercularis, Pcctu7iciilus 

 glycimeris, Mactra arcuaia, M. ovalis (soUda), Tellina obliqua, 

 T. crassa, T. prcrtenuis, Lucina horealis, Cai'dhim edule, C. angusta- 

 tiun, I\fy tikes ediilis, A^assa granulata, N. reticosa, Bucciniim nndattim, 

 and var. tencrum, Nalica catetia, N'. vmliipunctata, Purpura teiragona, 

 P. lapilhis, Liitorina liltorea, Turn'/ella incrassata, etc. The Echino- 

 dermata include Echinocyamus pusillus, etc., the Crustacea, Balainis 

 crenatus, and claws of Crab ; vertebroe of Fishes also occur. 



The total number of species of Mollusca from the Red Crag is about 273 ; of 

 these 240 are living, and 33 extinct species. Some land-shells of living British 

 and Continental species have been recorded.'' 



It has been noticed by Prof. Prestwich that, as we recede from the centre of the 

 district, the beds become almost devoid of shells, or they occur only in patches. 

 This is due in some cases to original absence, in others to dissolution. The subject 



^ Q. J. XXX. 403 ; Explan. Sheet 47 (Geol. Surv), p. 30. 



2 Proc. G. S. iii. 127. 



3 Q T- xxvii. 325. 350. 



* R. G. Bell, G. Mag. 18S4, p. 262. 



