100 
CHAPTER VIL 
.RED CRAG—continued, NORWICH CRAG, AND 
CHILLESFORD CRAG. 
Taking up the description of the Crag at the point where it 
was left at the end of last chapter, we find higher fossiliferous 
zones appearing north of the Butley River. The most southerly 
of the sections, tiiose at Chillesford, were discovered by Prof. 
Prestwich* during an excursion made for the purpose of ascer¬ 
taining “ whether the distinction of age introduced upon palaeonto¬ 
logical grounds, between the crags of Norfolk and Suffolk, could 
he confirmed by visible superposition.” More recently Prof. 
Prestwich has re-examined the pits, and the following notes are 
principally taken from his account.f 
The sections at Chillesford are three, two of them close to the 
Church, and the third in a brick-field half a mile to the east- 
north-east. The pit behind the Church and that in the stack¬ 
yard below the Church, furnish an almost continuous section. 
Prof Prestwich having proved by excavation the nature of the 
few feet of beds between the floor of the upper and the top of 
the lower pit. It must, however, be borne in mind that the 
latter pit is exposed to decalcification, from which the beds seen 
in the higher are exempt, for they are protected from the action 
of percolating water by an overlying mass of clay. The section 
exhibited by these pits is shown on the opposite page. (Fig. 22.) 
The great interest in thi.s section is that in the upper portion 
of the sand we find the Mollusca with their valves united and 
evidently on the spot where they lived. These tranquilly de¬ 
posited strata pass upwards, without a break, into the Chillesford 
Clay, and downward into the ‘‘ Scrobicularia Crag ” of S. V. Wood, 
which is probably a continuation of the Norwich Crag of Norfolk. 
About six furlongs to the east-north-east there is a sand-pit 
(marked on the Map) which S. V. Wood considers also to show 
this Chillesford Crag,” J and from these two pits he has collected 
a large number of mollusca. Northern shells are there much more 
abundant than in the lower beds, both in species and individuals, 
and a number of the common Red Crag forms seem to have 
disappeared. The three species of Tellina, T. lata, T. obliqua, 
T. 'prcBtenuis, so conspicuous around Norwich, occur in profusion. 
* Quart. Journ. Geol. Soc., vol. v., pp. 345-353. (1849.) 
f See also ibid., vol. xxvii., pp. 335-339. (1872.) 
X Ibid., vol. xxii., p. 544. (1866.) 
