Vol. 54.] AND THE CORALLINE CRAG. 337 



Between the Broom Hill pit and that in Sudbourne Park near the 

 Hall (No. 12), rather more than a mile to the north, the base of the 

 Crag dips still farther, its junction with the London Clay occurring 

 at the latter place at a depth of 31 feet (probably about 27 feet 

 below Ordnance datum). This boring took 4 or 5 days to complete, 

 the difficulty being to extract the loose and wet material. Unless the 

 hole is kept clear as the work goes on, the borer is set fast, and can 

 be regained only with great labour. There was a marked absence 

 of fossils at this spot, little else being brought up but comminuted 

 Crag. No seam of large shells was met with, the only recognizable 

 fragment being a small portion of the hinge of a Cyprina, from a 

 depth of 30 feet. The last foot or two of the Crag both here and in 

 other borings was of a bright blue colour.^ 



Exposures of the shelly sands in the Orford district are now 

 confined to the small area between this section and Butley Creek, 

 none being known to me to the north, except the small seam before 

 aUuded to in the Bullock-yard pit at Iken, Brick-kiln Earm 

 (No. 27). Prestwich stated, however, that beds belonging to 

 his zones D & E might be found at Iken ; but now the Crag 

 there exposed (with the above exception) is in the decalcified and 

 ferruginous condition of the upper part of the formation, that is, of 

 his zone G. 



The various sections of the altered Crag show the same difference 

 in character as do those of the lower and unaltered Crag. At 

 one pit it consists of fine material without fossils, except perhaps 

 an occasional valve of Pecten opercularis ; at another it is crowded 

 with the casts of large shells ; while at a third are found layers of 

 reef-building polyzoa in their natural position. 



I bored at the pit of ferruginous Crag at Sudbourne Park gates 

 (No. 14), finding comminuted material only, for nearly 20 feet, and 

 to a lower level than that at which the shelly sands occur at the 

 section near the Hall, but without reaching them. The surface of 

 the Crag at this pit (No. 14) is about 33 feet above Ordnance datum ; 

 adding to this 27 feet, the approximate depth below Ordnance datum 

 of the base of the formation at pit No. 12, just below, we can ascertain 

 with some approach to accuracy that its total thickness at Sudbourne 

 is 60 feet.^ It was from Sudbourne that three of the samples of 

 material, Nos. 5, 4, and 6, which were analysed by Messrs. Sutton, 

 were taken, the first being from the upper part of the indurated Crag 

 at section No. 14, the second from the shelly sand in the Hall pit 



These species, coming from the lowest part of the Crag, are all found at 

 higher levels in the immediate vicinity, and at Sutton. At this spot univalves 

 are equally scarce in the 20 feet of Crag above, and in the 20 feet below the 

 water-level, while at the Gomer pit, less than a mile distant, as we have seen, 

 they are very abundant in the same stratigraphical position. If the Gomer 

 beds, containing univalves abundantly, were continuous, we ought to have met 

 with them at other localities in some of our borings, which was not the case. 



1 See p. 323. 



^ This was the estimate originally made by Mr, Wood and myself in 1872, 

 Suppl. ' Orag Mollusca,' Introd. p. iii, Monogr. Palaeont. Soc. Prestwich's 

 figures are 83 feet. 



2b2 



