part 1] aAULT ajs^d lower greexsajs'd is^ear letghto]S". 61 



Sands immediately below the Mammillatus beds at Grrovebmy 

 (fig. 17), Chamberlain Barn (fig. 16), and in one or two places at 

 Nine Acre are quite different in aspect from the fossiliferous 

 nodules of the ovei'hdng beds, and have as yet yielded no fossils, 

 whatever, except some vague tubular markings. They are generally 

 composed internally of a dense smooth phosphate, pale buff,, 

 dee^Dening centrally to dark grey or blackish, but often mottled 

 with crimson patches, while outwardl}" they merge without definite 

 boundarj^ into their sandy matrix. They may represent only the 

 effect of phosphatizing solutions percolating into the sands from 

 the overlying beds ; but in some places, particularly in the section 

 shown in fig. 17, they appear to form a distinct band, separable- 

 from the beds above and below. They are only seen where the top 

 of the Sands has been protected from weathering b}"" a fairly thick 

 cover of Basement beds, with which they are certainly in some way 

 connected. When they first made their appearance, some years- 

 ago, in the Grovebury sections, I thought that they might prove 

 to be the local equivalents of the Shenle}^ limestone-len tides, but 

 in the absence of fossils no such proof is forthcoming. 



The ferruginous components, so conspicuous in the Basement 

 beds farther north, are represented at Grovebuiy onh^ by occasional 

 waterworn Hat fragments of iron-grit (the largest to come under 

 my observation being 6 inches in diameter), presumably derived 

 from the shoal on the north, and by a few small iron boxstones. 

 and thin wisps of imperfect ferricrete. These are the final indi- 

 cations of the fading-out of the breccia. 



The correlation of the Grovebury and Chamberlain Barn sections, 

 is beyond question (figs. 17 & 16). The pronounced breccia-band in 

 the latter marks the closer proximity of the shoal-reef, and proves 

 its pre-existence and sharp erosion during an early stage in the 

 accumulation of the nodule-beds. The large slabs of iron-grit 

 and other detrital material of the breccia are set in a matrix of 

 gritty glauconitic loam indistinguishable from that of the over- 

 lying beds, and phosphatic nodules occur occasionally in the breccia 

 as well as above it. The patches of calcrete and the iron box- 

 stones are further indications of its approach to the condition of 

 the irongrit-breccia of Shenley, and the only marked difference is 

 the absence of unbroken tabular iron-pan. All the circumstances, 

 point to the coarse material having travelled down the sloping 

 floor of the sea from no great distance, and having come to rest in 

 deeper water. Just as the Grovebuiy type of deposit has its; 

 closest lithological analogue in the Mammillatus Beds of the- 

 Argonne, so the breccia-band of this and other sections has its 

 nearest physical analogue in the ' Tourtias ' of the Flanders, 

 country, these ' Tourtias,' as their investigators have long recog- 

 nized, marking a condition of accumulation and not a fixed time. 



From the Chamberlain Barn section we pass to the old south- 

 western working at Shenley (Garside's pit, figs. 4 & 12, pp. 11 & 

 22) about 1100 yards distant, and find here a cleaner calcareous- 

 glauconitic sand, devoid of large nodules, with a strong 'pan '-bound. 



