Of the marine shells, 124 in number, about 18 per cent are extinct, according to the latest estimate given me by Mr. Searles Wood; but, for reasons presently to be mentioned, this percentage must be only regarded as provisional. It must also be borne in mind that the proportion of recent shells would be augmented if the uppermost beds at Bramerton, near Norwich, which belong to the most modern or Chillesford division of the Crag, had been included, as they were formerly, by Mr. Woodward and myself, in the Norwich series. Arctic shells, which formed so large a proportion in the Chillesford and Aldeby beds, are more rare in the Norwich Crag, though many northern species—such as _Rhynchonella psittacea, Scalaria Grœnlandica, Astarte borealis, Panopæa Norvegia,_ and others—still occur. The _Nucula Cobboldiæ_ and _Tellina obliqua,_ Figs. 119 and 120, before mentioned, p. 194, are frequent in these beds, as are also _Littorina littorea, Cardium edule,_ and _Turritella communis,_ of our seas, proving the littoral origin of the beds. OLDER PLIOCENE STRATA. Red Crag.—Among the English Pliocene beds the next in antiquity is the Red Crag, which often rests immediately on the London Clay, as in the county of Essex, illustrated in Fig. 121. Fig. 121: Red Crag, London clay and chalk. It is chiefly in the county of Suffolk that it is found, rarely exceeding twenty feet in thickness, and sometimes overlying another Pliocene deposit, the Coralline Crag, to be mentioned in the sequel. It has yielded—exclusive of 25 species regarded by Mr. Wood as derivative—256 species of mollusca, of which 65, or 25 per cent, are extinct. Thus, apart from its order of superposition, its greater antiquity than the Norwich and glacial beds, already described, is proved by the greater departure from the fauna of our seas. It may also be observed that in most of the deposits of this Red Crag, the northern forms of the Norwich Crag, and of such glacial formations as Bridlington, are less numerous, while those having a more southern aspect begin to make their appearance. Both the quartzose sand, of which it chiefly consists, and the included shells, are most commonly distinguished by a deep ferruginous or ochreous colour, whence its name. The shells are often rolled, sometimes comminuted, and the beds have much the appearance of having been shifting sand-banks, like those now forming on the Dogger-bank, in the sea, sixty miles east of the coast of Northumberland. Cross stratification is almost always present, the planes of the strata being sometimes directed towards one point of the compass, sometimes to the opposite, in beds immediately overlying. That such a structure is not deceptive or due to any subsequent concretionary rearrangement of particles, or to mere bands of colour produced by the iron, is proved by each bed being made up of flat pieces of shell which lie parallel to the planes of the smaller strata.