THE JURASSIC DEPOSITS WHICH UNDERLIE LONDON. 739 
the period of the deposition of these rocks, and not to have been 
derived from any older formation. 
Prof. T. Rupert Jones, F.R.S., who has kindly examined these 
microscopic forms for me, has detected the following species :—— 
Ostracoda. 
Macrocypris Bradiana, sp. n. 
Cythere Schwageriana, sp. n. 
Cythere juglandica, sp. n. 
Cythere (Cythereis) quadrilatera, Rom. 
Cythere, sp. 
Foraminifera. 
Cristellaria rotulata, Lan. 
Cristellaria cultrata, Montf. 
Cristellaria, sp. 
Lituola depressa, sp. n. (probably derived). 
Of these minute fossils Prof. T. Rupert Jones remarks that there is 
nothing particularly characteristic of any formation, similar forms 
ranging through Secondary, Tertiary, and Recent times. 
At a depth of 14 ft. below this clay-band there occurred a thin 
layer of pyrites about half an inch in thickness, almost completely 
made up of small rounded or oval particles with a polished surface. 
Three feet lower we reach a very remarkable ‘“ junction-bed ” 
containing phosphatic nodules like those in the bed at the base of 
the Gault. 
This junction-bed, which is only 6 in. in thickness, is of very 
peculiar character. Its matrix consists of clay containing many 
oolitic grains and fragments of fossils. Scattered through this clay 
are many subangular and rounded fragments, some of them of 
considerable size, of a micaceous sandstone, strikingly like that of 
the Coal-measures, of quartzite and indurated sandstone, of sub- 
erystalline limestone, and of other hard rocks, with some particles of 
anthracite. Intermingled with these are a number of phosphatic 
nodules, one of which, analyzed by Dr. Percy Frankland, yielded 
27-06 per cent. of phosphoric anhydride. 
That the matrix of this remarkable “ junction-bed” was derived 
from the denudation of the underlying Great-Oolite deposits, there 
cannot be the smallest doubt. Waterworn fragments of the oolitic 
limestone, oolitic grains disengaged from their matrix, and recog- 
nizable, though much waterworn, with Jurassic forms of Brachiopoda 
and Bryozoa, abound in it. Fragmentary and waterworn teeth of 
Lamna, Pycnodus, Hybodus, and other Jurassic genera of fish, with 
fragments of spines and teeth too imperfect for recognition, also 
occur in it in great numbers. The only fossils in the bed which 
were not manifestly derived were a few Foraminifera and Ostracoda. 
The foreign rock-fragments in the mass appear to have been 
certainly derived from Paleozoic deposits, which must have been in 
