Vol. 54.] AND THE COEALLINE CKAG. 347 



My theory of the Coralline Crag is simpler than Prestwich's. 

 I not only believe with him that in the upper part, but that in 

 the whole of the formation we have the remains of a series of 

 submarine banks. This view, first suggested by Mr. Wood, Sen., 

 in 1863^, has since been adopted by Mr. C. Reid.^ I doubt, 

 however, whether these banks originated ' far from shore,' as 

 the latter writer is inclined to think. The bed, a foot thick, 

 observed by Prestwich at Sutton (his zone A) was evidently accu- 

 mulated under conditions different from those of the rest of the 

 deposit, representing the commencement of the re-invasion of East 

 Anglia by the sea. No trace of any stone-bed was met with in 

 any of the six borings at Gedgrave and Sudbourne in which ^the 

 London Clay was reached, but this is not conclusive that no such 

 bed exists there, as the borer might possibly in every case have 

 failed to strike a stone, and the nodule-bed certainly occurs at 

 Boyton, only a mile distant from one of them, on the south side of 

 Butley Creek. It seems to me that, with the exception of this 

 thin basement-bed, the Coralline Crag from top to bottom was 

 deposited under more or less uniform conditions, in water suffi- 

 ciently shallow to be within the reach of currents, at no great 

 distance from the margin of the Crag sea, and in banks which were 

 probably parallel with it. Notwithstanding the slight differences 

 noted by Mr. Sutton between the different samples submitted to 

 him, differences not greater than those to be observed in contiguous 

 parts of the sea-bottom at the present day, the material of which 

 this formation is composed has essentially the same character 

 throughout ; and if this be so, it seems that little deposition of sedi- 

 ment took place in the Crag area (or that it was afterwards removed 

 by current-action), until those conditions were established which 

 caused the accumulation of the banks postulated by my theory. 



I see no reason for supposing that these conditions differed 

 greatly from those now existing in the German Ocean, or in the 

 shallow seas surrounding the British Isles, except that they were 

 associated with the prevalence of a warmer climate. The present 

 may thus throw light on the past, and if we cannot absolutely 

 restore the geographical features of the Coralline Crag period, we 

 may at least picture to ourselves generally the circumstances under 

 which it must have originated. 



In the first place, there is no evidence that beds of dead and 

 drifted shells are now being laid down simultaneously in British 

 Seas over large and continuous areas. Deposits of shelly sand may 

 accumulate, however, in at least two ways : as submarine banks, 

 limited in extent and caused by current-action, or as littoral drift. 

 The former seems to me to represent the conditions attending the 

 deposition of the Coralline Crag, the latter those under which the 

 different Eed Crag beds originated. Two examples of the first may 

 be given. 



' Quoted in ' Foraminifera of the Crag,' Monogr. Palaeont. Soc, Introd. p. ii 

 (1866). 

 2 Mem. Geol. Surv. 1890, ' Plioc. Deposits of Britain,' p. 41. 



