418 Walter Keeping—The Upware and Potton Pebble-beds. 
also markedly smaller at Upware, so that there is much reason to 
believe we are here further from the source of the pebbles than at 
Potton. 
Amongst the non-phosphatic fragments we find the same tile-like 
fragments of ironstone, pebbles of dark grit, and other relics of an 
older Neocomian deposit as at Potton; of the Jurassic rocks, frag- 
ments from the underlying Coral Rag are most conspicuous, especially 
in the basement bed. Of the pebbles of more ancient rocks we 
also find the same prevailing types as at Potton; vein-quartz and 
quartzite are especially abundant, also chert of many varieties. The 
indurated argillites are also common, and jasper is occasionally found. 
Some fragments of a pale micaceous laminated grit occur, which 
may well have had the same origin (Upper Cambrian or base of 
Silurian, Sedgwick) as the specimens 7 and k from Potton. 
Other Localities.— Following the outcrop of the Upware and 
Potton ironsand series southwards to Brickhill and Farringdon, the 
same small pebbles of quartzite, chert, and Lydian stone occur, vein- 
quartz being most abundant at the latter place. Again, at. Godal- 
ming and Folkestone quartz pebbles are abundant, and the “ dark- 
coloured shiny stones” of Mr. Meyer' appear to be our cherts and 
Lydian stones. In the Lower Greensand of Redcliffe and Shanklin, 
Isle of Wight, there occur irony grit, compact quartzite, reddish 
quartzite and jasper. 
Thus we find that a certain set of pebbles characterizes the Upper 
Neocomian beds of the East and South of England. A more 
remarkable fact is, that in the Neocomian rocks of North Germany 
we again find the same set of pebbles, including the characteristic 
subangular polished chert fragments and the phosphatic nodules. 
The Neocomian rocks of Berklingen and Shoeppenstadt, near Bruns- 
wick, contain beds of calcareous conglomerate with phosphatic 
nodules, irony fragments, and subangular chert, scarcely distinguish- 
able in general appearance from the Upware conglomerate. 
The Portlandian conglomerate of the country around Swindon 
must also be noticed here, on account of its included pebbles. This 
bed, which is well seen on Bourton Hill, is a calcareous conglome- 
rate with scattered pebbles very similar in appearance to the Upware 
conglomerate. The pebbles are almost exclusively chert, mostly 
dark coloured, some jaspery. J have not been successful in the 
search for organisms in them under the microscope. Pebbles of 
syenite, greenstone, chert (?) and other rocks are described from the 
See beneath the Gault, discovered in the Kentish Town 
oring. 
The original homes of the pebbles.—In the unpublished work before 
referred to, I discuss the origin of the phosphatic and other Neoco- 
man pebbles, and come to the conclusion that while some of them 
(Ammonites deshayesit, Endogenites, as also many of the indigenous 
species) seem to be of southern origin, others, namely, the dark grits 
with fossils, point to northern deposits, such as the Lower Neoco- 
mian sands of Tealby, as their original home. 
1 Geol, Assoc. Report Dec. 4, 1868. 
