494 [Dec. 18' 



covered in these pipes any mammalian bones, nor have I learned 

 that any such discovery has been made by others. 



I have now to describe some sand-pipes near Norwich, not in ; 

 solid chalk, but in reconstructed chalk or chalk- rubble. j 



The pit in which these occur is at Crostwick, about five miles' 

 N. E. of Norwich, on the western side of Rackheath Valley, and 

 at its point of confluence with the valley of the Bure. The di- 

 mensions of the pit are about 35 yards by 48 and the sections of 

 its southern, eastern, and western sides, are represented in the 

 three following diagrams : — 



Fig. 10. Crostwick Pit. 

 South. 



East. 



West. 



Fig. 11. 

 East 



North. 



South, 



Note. — The references to the above three diagrams are as follows : 



a, b, c, d. Various layers or seams of flint in the gravel and sand overlvine 

 the chalk ( Uncallow). \^ 



e. A pipe which divides into two cylinders. 



/. A flint protruding from the chalk into a sandpipe. 



g. Various flints (not in layers) in the uncallow. 



Various irregular seams of clay also occur in difl^erent parts of the uncallow, as 

 near e in fig. 10. (to the right of that letter); to the left of/ in fig. 11. ; and 

 where lines are represented in fig. 12. 



Seams of crag shells also occur at two or three points near h in fig. 10. and 

 above /in II. 



The lowest line of flints, marked a, a, runs with great regu- 

 larity all round the pit ; and must, I think, be in solid undisturbed 

 chalk. The next line {b, b) is less regular and continuous; but it 



