346 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [MaV. 7, 



the niammaliferous crag exhibiting a group of fossils, a large propor- 

 tion of which are of estuary, fluviatile, and land origin, whilst that of 

 the red crag is in greater part marine, added to the very disturbed 

 aggregation of strata of the latter, caused us to entertain some doubts 

 as to whether the conditions under which they were respectively ac- 

 cumulated might not have so modified their faunas as to render 

 conclusions, however able, drawn from a comparative estimate of 

 such faunas, of uncertain value owing to the want of parallelism in 

 the data. This therefore presented a case in which the test of super- 

 position appeared desirable. 



Small and ill-exhibited patches of the mammaliferous crag had 

 been traced at distant intervals from the neighbourhood of Norwich 

 to Thorp Common, two miles north of Aldborough, thus ending ap- 

 parently near to where the coralline and red crags set in. We 

 therefore here commenced our examination of this district, and in the 

 course thereof we were fortunate enough to meet with a bed of a 

 character unusual in the Crag districts, and which, although it does 

 not settle the question we had proposed to ourselves, is of much in- 

 terest both in its physical conditions and in its organic remains. 



The course we first took was from Aldborough in a south-westerly 

 direction towards the parish of Iken (see map, p. 345), and at a 

 distance of a mile to a mile and a half from the ferry over the Aide, 

 we reached several pits of the ordinary coralline crag, which here 

 rose in a low ridge of hills on the borders of the sea-marshes. 

 Thence turning northward we crossed a small valley, and in ascending 

 the opposite hill noticed a pit in a field to our left, and close adjoin- 

 ing the eastern side of a farm-house which stands exactly by the 

 Ordnance map two miles due west in a straight line from the Martello 

 tower immediately south of Aldborough. At a short distance this 

 pit presented the appearance of yellow sands overlaid by the common 

 bluish grey great clay drift of the district, but on a nearer approach 

 we found it to consist of finely laminated micaceous clays, with im- 

 pressions of shells, overlying light yellow sands, also with impressions 

 of shells of the genera M^/a, Tellina, Nucula and Cardium ; but the 

 impressions, or rather casts, were so friable that they could not be 

 removed, and only in a few cases were Mr. Morris and Mr. Austen 

 able to determine, with some doubt, the species which apparently 

 would agree with those we afterwards met with at Chillesford. 



There were no beds of the red or coralline crag here exposed 

 whereby the relations of this deposit might be ascertained. From 

 the outline of the country, and from the occurrence of a pit of coral- 

 line crag at a short distance to the south-east and on a rather lower 

 level on the hill, this latter deposit appeared to pass below these fos- 

 siliferous clays and sands, — a supposition shortly confirmed by another 

 section at Iken brick-field, about a quarter of a mile further northward 

 and on the same level. (See fig. l,p.347, and Sections, fig. 3, p. 349.) 



We here have the direct superposition of the fossiliferous clays and 

 sands "&" and *'o" on the coralline crag "e." There is however 

 no passage between them. Although in apparent conformable stra- 

 tification, they are separable in structure. The surface of the semi- 



