1865.] PISHEE CHILLE8F0RD BEDS, 25 



village of Thorpe. The spread of these sands generally obscures the 

 subjacent rocks, but by a valley- denudation the Norwich Crag is 

 exposed at the one spot described ; and I believe the top of the 

 Chillesford Clay to be also exposed for a short distance. To the 

 presence of this clay I attribute the water which is found in the pit 

 close by the shell-pit. The sands would not support water. 



The stratification of the district strongly favours the view I have 

 taken of the superposition of the Norwich Crag upon the Chillesford 

 Clay. On the other hand, it would be quite possible to conceive 

 that the Mya-bed might be here expanded into a thick bed of Crag, 

 and this is what has been generally assumed to be the case. I 

 think, however, that the evidence rather supports my suggestion. 



In the first place, the assemblage of species as seen at the shell- 

 pit differs from that of the Mya-bed. As strongly as I felt convinced 

 on the spot that the Crag above Ferry-farm was derived from the 

 Mya-bed, so strongly did I feel that the Crag at Thorpe was not de- 

 rived from it. 



In the second place, the pebbles of indurated clay found at the 

 bottom of the shell-pit exactly correspond in composition and colour 

 with the Chillesford Clay, wherever it is weathered brown, as, for 

 instance, at Chillesford itself. 



In the third place, I have always noticed a porous sand under- 

 lying the Mya-bed, which would not support water. Indeed, in the 

 clay pit near Sudbourn Park I have mentioned that a run of water 

 from a field-drain is conducted to this sand and immediately lost in 

 it. If, therefore, the Thorpe Crag were on the horizon of the Mya- 

 bed, I do not think that we should have a spring at its base, nor a 

 pond close by in the subjacent stratum. 



The conclusion then appears to be correct, that the Fluvio-marine 

 Crag at Thorpe near Aldborough rests on the Chillesford Clay, and 

 that the descending sequence in that district is — 



1. Fluvio-marine or Norwich Crag. 



2. ChiUesford Clay. 



3. Mya-bed resting on sands, which, as at Aldborough Gas- 



works, are occasionally fossiliferous. 



4. Red Crag. 



Let us now see whether this sequence is borne out by other expo- 

 sures of these beds. 



It has long been known that a formation containing, as Sir 

 Charles Lyell tells us, " lamellibranchiate shells with their valves 

 united, mixed with land and freshwater Testacea, and with the 

 bones and teeth of Elephant, Ehinoceros, Horse, and Deer"*, occurs 



* Elements, 1855, p. 156. Since this paper was read I have been favoured 

 with the sight of a letter written in 1864 by Col. Alexander to Mr. Searles V. 

 Wood. Putting the contents of this letter by the side of the information I have 

 received from Mr. Ewen, I gather that four Mastodon teeth have been obtained 

 on this coast. That which is figured by Professor Owen in his ' Fossil Mammals ' 

 was found on the beach at Sizewell Gap, near Thorpe. Another, which Mr. 

 Ewen now possesses, was found under the cliff after a fall at Easton Bavent, 

 A third, with part of the jaw attached, was seen by Col. Alexander in the talus 



