Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/684

 though no strata represent this Diestien period, yet the Cetaceans, Sharks, and shell-containing Sandstone-nodules of the Suffolk bone- bed, are the fragments rescued to us from the destruction of a vast extent of a once existing close equivalent of the Black " Crag " of Antwerp. Such remains were long confounded with those belonging to the true Crag epoch. They can now no longer be so. The term " Crag " is not applicable to the Cetaceans of the Diestien period, nor to the other contents of the Suffolk bone-bed.

The observation of the occurrence of the Suffolk bone-bed below both Coralline and Red Crags, and the recognition of tbe Diestien age of a large portion of its contents, first published by me in 1865, and the similar conclusion of the Rev. John Gunn with regard to the Mastodon and Elephas supposed to belong to the Norwich Crag proper (but which he has shown to be confined to a basement bed, the Norfolk stone-bed), have facilitated very considerably the comparison of the Norfolk and Suffolk shell-bearing strata. Mr. Prestwich, after detailed study of the stratigraphical and palaeontological evidence, has recorded his opinion that the Norwich Crag is the true continuation northwards of the Red Crag of Suffolk. At the same time, he assigns an earlier age to the Coralline Crag, and points out a lower undisturbed and an upper disturbed portion of both Red and Coralline Crags in the Suffolk area.

The remarkably confused condition of the Red Crag in Suffolk tells a history which enables us to understand in some measure its agreement with and its differences from the Norfolk Crag. Many remarkable species of Mollusca, such as Valuta Lamberti, Cassidaria bicatenata, Pleurotoma intorta, &c, occur in the Red Crag, but do not appear in the so-called Norwich Crag ; and no valid evidence has been adduced to support the view that they are derived from the Coralline Crag when found in the Red. At the same time, the more boreal fauna of the Norwich beds is present in the Red Crag. It is well known to collectors of the mollusca of the Red Crag in Suffolk that, superficially, they may only expect to obtain the shells belonging to the Norwich-Crag fauna, and that for the rarer forms, such as those mentioned above, they must seek in the deeper parts of the deposit and in the low-lying areas. Thus, at Waldringfield, and in the immediate neighbourhood of Woodbridge, lying on the river Deben, those species of the Red-Crag Mollusca are to be obtained which do not occur in the Norwich deposit; moreover, in these localities the valves of Lamellibranchiates are frequently found in apposition *, and small specimens of a well- marked variety of Terebratula spondylodes (differing from the Coralline-Crag variety), with united valves, are not uncommon. From this we may infer that the Red Crag is a deposit representing a considerable stretch of time, and that its earliest deposited beds contained a fauna differing from that which occupied the sea which at later periods, again and again, turned over and added to the accumulation. At the earlier period the Red-Crag sea contained a fauna not very different from that exhibited in the Coralline Crag, still retaining


 * See a paper by Mr. Alfred Bell, Brit. Assoc. Rep. 1868.