544 PROCEEDI>'GS OP THE GEOLOGICAL SOCIETY. [JuilC 20, 



afforded by the Crag of Butley, which I have now to mention. It will 



he convenient for reference if I designate this as the Sutton Crag. 



The district intervening between the banks of the Deben and the 

 exposure of the Eed Crag around Butley is occupied by high heath- 

 land formed of the sands interposed between the Crag and Boulder- 

 clay ; and, the coast-line corresponding to it being low, we have no 

 recurrence of the Eed Crag until we come upon that exposed by the 

 denudation of the Aide valley around Butley, Chillesford, and 

 Sudboum. The Crag there, although in physical structure entirely 

 resembling that between the Deben and the Stour, possesses a 

 dissimilar fauna. In it there are, however, many of the forms 

 which characterize the Sutton Crag ; yet they are subordinate to 

 those of northern aspect, which begin here to preponderate. For 

 instance, although Pectunculus glycimeris, which is so abundant in 

 both the Walton and Sutton horizons, is present, and in the lower 

 part of the Butley Crag not uncommon, yet it becomes subordinate 

 to such forms as Tellina ohliqua, T.prcetenuis, and Cyprina Islandica, 

 which here begin greatly to prevail. In the upper portions of this 

 Crag, namely that upon which at Chillesford and Tunstall Heath the 

 Scrobicularia-crag rests, this feature is yet more marked, and the 

 Pectunculus becomes a rare shell, while My a truncata, Tellina ohliquxi, 

 T. prcEtenuis, T. lata, Cyprina IsUuulica, and Macira ovalis, which 

 form an enormously preponderating proportion of the Chillesford 

 bed (e of diagram), become especially abundant. This is the Crag 

 which is found at the base of the pit below Chillesford church, in 

 several of the pits in Butley j)arish, and in that one pit near Sud- 

 boum church in which the Eed Crag is seen resting on the Coralline. 

 It also occurs in a run-down pit upon Tunstall Heath. 



Besting upon this Crag, in the pit under Chillesford church, 

 occurs the uppermost portion of the Eed Crag. It is slightly oblique 

 at the base, but becomes horizontal in its upper beds, gradually losing 

 that red colour to which the Eed Crag owes its name. The actual 

 horizon at which this Crag sets in is marked in a distinct manner 

 by the incoming of a shell not yet found in the lower horizon, namely 

 Scrobicularia piperata. This shell, although thus abruptly appearing, 

 occurs in profusion, and in association almost exclusively with those 

 forms which greatly preponderate in the Chillesford beds, namely Cy- 

 prina Islandica, Mactra ovalis, Tellina ohliqua, T. lata, T.pratenuis, 

 and J/yrt truncata. These shells form almost the entire fauna of the 

 uppermost portion of the Eed Crag, sho^ving a great contrast to the 

 richer fauna of the older horizons. The Scrobicularia again becomes 

 extremely rare in the Chillesford beds. Only one other pit is known 

 to me in which this Crag occui's : it is on Tunstall Heath, distant 6 fur- 

 longs N.E. by E. from Chillesford church, marked on the Ordnance 

 Map ''Sandpit." Divided from this Crag by only about 4 or 5 feet of 

 brown sand, occurs the tnie Chillesford bed described by Mr. Prest- 

 wich in 1849, and industriously searched by me afterwards. The 

 fauna derived from this bed (e of diagram) and from the other ex- 

 posures of the same formation in northern Suffolk is contained in 

 the subjoined list : — 



