Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/234

120 of Bryozoa, including the Salicornaria sinuosa, which I found here in greater abundance and more perfect preservation than at any other spot. It also contains dark green grains of silicate of iron, dispersed and in seams. The globose Fascicularia and Alveolaria are common in both e and f.

In strong contrast with this lower bed is the overlying ferruginous soft rock, which forms the upper part of this quarry. It consists essentially of comminuted shells and of fragments of Bryozoa, and often shows oblique lamination. This mass, which here is about 11 feet thick, is cemented together, partly by carbonate of lime, and at this spot partly by the oxide of iron, and forms a soft and very porous dark brown rock. Detached valves of Pectens and other shells, and a considerable number of Fasciculariæ and Alveolariæ are found entire, together with remains of Crustacea and Echinodermata. This bed at Sutton is but 11 feet thick, forming only the lower part of the upper division of the Coralline Crag. It is more largely developed in the neighbourhood of Sudbourne, where it attains a thickness of 20 feet. At Low Gedgrave there is a pit where it is nearly 30 feet thick. This division of the Crag often presents numerous curious instances of oblique lamination, and exhibits, in fact, a very instructive illustration of the frequent reconstruction of old shell-banks. Altogether the series of beds at and around Sutton and Sudbourne, especially some in the near vicinity of Sudbourne church (as in fig. 3), are of the greatest interest.

This division is generally very uniform in its composition. There is a pit, however, at the corner of the two cross-roads, 6 furlongs N.N.E. from Sudbourne Church, where the upper 6 feet consists of finely comminuted shells, with a few Bryozoa.

This completes the series of beds forming the two divisions of the Coralline Crag. I have denoted them by letters, for the convenience of correlation with the same beds in other parts of the district.

The thickness of the lower division of the Coralline Crag, as proved at Sutton, is about 47 feet, and that of the upper division, as it exists in the neighbourhood of Sudbourne and Gedgrave, about 36, making a total of 83 feet.

Taking the whole together, the general section of the Coralline Crag is as follows (fig. 4):—