24 ME. G. W. LAMPLVGH OX THE JVyCTIOX OF [vol. Ixxvili, 



[PosTSCEiPi. — Later excavations revealed, during the summer 

 of 1921, a tapering lenticle o£ fossiliferous limestone of the Shenle}"" 

 type, enwrapped above aiid below bv hard iron-pan, in the upper 

 jDart of the iron-grit breccia (3) at the southern corner of the 

 western face of the pit. The lenticle, at its maximum, was 3| feet 

 long and 7 inches thick, of which the inner 4 inches was pinkish 

 and iron-stained gritty limestone. The limestone was rendered 

 soft and crumbly by weathering, like most of the smaller patches 

 at Shenley, and the fossils were consequently in a poor state ; I 

 obtained the casts of several small Terebratnlse and Ehynchonellids, 

 a small Aviciila and portion of an Echinoid-spine — all forms 

 common at Shenle}'.] 



Section at the north-western corner of Double Arches pit, 

 5 yards north-west of The Poplars; September 27t h, 1920. 

 Surface, about 360 feet O.D.. with a strong slope east- 

 wards at right angles to the section. 



TJiicJoiess in feet. 

 Z. Soil, passing down into structureless sandy loam (downcreep and") ^ 



wash) with an occasional Hint or otber stone in the upper part. ) 

 2. The Silty beds : — 



c. Interstratilied dull dark-green and brownish loams, evenly"^ ") 



bedded as a whole, but the individual layers wispy, wavy, and | 

 inconstant : streaked with imperfect ferruginous concretions l 3 j. -i 

 in thin tables along clayey bedding-planes, running in places f * 

 into tabular clay-ironstone lenticles, best developed along the j 

 base and in the upper part of (b). J . 



b. Fine-grained ver\' dark-green streaky loamy sand, traversed*^ j 



b}' faint tubular markings ; a thin sprinkling of coarse | ' 



polished grit in the lower part, with rare particles up to f inch \ ■, , ^ 

 in diameter; a few wide-spaced hollow ironstone nodules more [ 

 or less globular, in the lower part ; and an impersistent band | 

 of tabular flaky ironstone at the base. J 



a. Euff-coloured and rusty ferruginous loams; streaked with"\ 



brown and gre\- unctuous silt and clay, which predominate ( „| . i. q 

 towards the base, and throw out water : base uneven, with C 

 small and lar^e undulations. J J 



1. Rather coarse Silver Sands, with rusty buff and coffee-coloured 



streaking and staining at the top and towards the base about 20 



Finer-grained sands of lower grade proved below. 



The full thickness of the Silty beds (2) has not yet been reached 

 in the Double Arches pit, and may prove to be as great as at 

 Miletree Farm (fig. 11, p. 20). Their quick reduction to less than 

 2 feet in the neighbouring PoiDlars Pit shows that here again, as in 

 the Shenley group of sections, they have a Avedge-like outline, which 

 suggests that they fill hollows, partly original and partly of erosion, 

 among the cross-bedded sand-banks of the coarse clean Silver 

 Sands. They have, however, also been pared down, along with the 

 coarse sands, at the close of Lower Cretaceous times. I saw no 

 fossils, except small carbonaceous fragments, in these beds, and 

 no phospliatic nodules. The section in the Silty beds is continued 

 southwards, showing minor variation only, for over 100 yards ; also 

 at right angles, eastwards from the northern end, for 20 or 30 

 yards, until cut out by the slope of the little valley ; but in other 

 parts of the pit, the Silver Sands reach to the top. 



Y'o 



