A HISTORY OF SUFFOLK 



of which are sometimes filled with calcareous veins. Beds of this 

 character have been used for building purposes, as in the tower of 

 Chillesford church ; they have been quarried like a freestone, and perhaps 

 on this account the name 'crag' may have been introduced into East 

 Anglia. Blocks also have been obtained from the ' Thorpe Rocks ' on 

 the beach near Aldeburgh. 



The stone beds do not yield the rich variety of mollusca found in 

 the loose sands, but this, as pointed out by Mr. F. W. Harmer, is owing 

 to the fact that the shells have been largely dissolved away by the action 

 of acidulated water. Consequently the sub-divisions made in the Coral- 

 line Crag by Prestwich are not to be regarded as successive zones, but 

 rather as altered local conditions in the strata. In proof of this Mr. 

 Harmer has pointed out that at Brick-kiln farm, Iken, a lenticular patch 

 of the shelly sands occurs in the midst of a mass of the indurated beds.^ 



The Coralline Crag attains a thickness of 50 or 60 feet, and from 

 its pale buff tint it has sometimes been termed the White Crag, in dis- 

 tinction from the Red Crag which overlies it. At some depth below 

 ground all the Crag beds are usually grey in colour. The principal 

 exposures of Coralline Crag are at Tattingstone, south of Ipswich ; at 

 Sutton and Ramsholt, south of Woodbridge ; and at Gedgrave, Sud- 

 bourne, Orford and Aldeburgh. From the abundance of fossils at 

 Gedgrave the formation has been termed the ' Gedgravian ' by Mr. 

 Harmer, and characterized as the zone of Mactra triangnla. 



Among the more abundant and noteworthy fossils are Cardita senilis, 

 Pectunculus glycimeris, Cyprina islandica, C. rustica, Astarte omalii, Diplo- 

 donta rotundata, Nucula nucleus, Pecten opercularis, P. tigrinus, Trophon 

 consocialis, T'urritella incrassata, Calypraa chinensis. Valuta lamberti, etc. 



At the base of both Coralline and Red Crag, but chiefly below the 

 Red Crag, there occurs a remarkable nodule and pebble bed which has 

 yielded numerous derived fossils, many of them phosphatized. It is 

 well known as a ' Coprolite bed,' and will be referred to more particu- 

 larly in reference to the Red Crag. It forms a layer 12 to 15 inches 

 thick beneath the Coralline Crag at Sutton, and has there yielded pebbles 

 of quartz, quartzite, flint, septaria from the London Clay, bones of 

 Jurassic saurians, and a large boulder of red porphyry, weighing about 

 a quarter of a ton." Coprolites were worked at this locality for a short 

 period. The most interesting fossils are those enclosed in rolled frag- 

 ments of sandstone and known as ' boxstones.' They include Valuta 

 auris-leparis, Conus dujardini, Nassa conglobata and Isocardia car (and var. 

 lunulata), and these with other forms characterize an older Pliocene 

 deposit, no longer existing in situ in this country. The boxstones, which 

 thus represent remnants of an earlier fauna than the Coralline Crag, have 

 been locally used for road metal. The fauna of the Coralline Crag, as 

 observed by Lyell, indicates a warmer temperature than that of the later 

 stages of the crag. The sea was open to the south, and the mollusca 



' Proc. Geol. Asioc. xv. 436, xvii. 424. 

 • Prestwich, Quart. Joum. Geol. Soc. xxvii. 117 ; E. Ray Lankcster, ibid. xrvi. 493. 



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