1898] PROBABLE DEPTHS OF THE GAULT SEA 309 
Folkestone. The specimens from Westwell Leacon and Godstone 
are still clays, with no colouration, the tubular infillings being bluish 
grey, whilst the Folkestone specimen is a clay ironstone. 
It is noteworthy of Zone III. at Folkestone, that owing to the 
absence of pyritous infilling of the foraminiferal shells, they are 
much paler in colour than is usual with Gault specimens of 
foraminifera. : 
The conditions in this zone seem to have been favourable for 
the crustacea, and by their abundance this bed is known to collectors 
of fossils as the ‘ Crab bed.’ At this horizon Ostracoda are especially 
abundant. Globigerina cretacea also forms a fairly large proportion 
of the washings. 
From the evidence of the foraminifera, the depth of this deposit 
was 1180 fathoms. 
The character of the clay makes it appear to have been originally 
a red mud of a semipelagic nature. 
Zone IV.—The clay of this zone is greenish grey. The foramini- 
fera are very minute, owing to the prevalence of muddy matter, and 
the scarcity of dissolved calcareous material. 
This clay is probably represented in modern deposits by blue 
mud rather than green mud, since glauconite, although present, is 
only in a small proportion in the washings. 
The depth determined for this zone is 840 fathoms. 
Zone V.—A_ grey-blue clay spotted with lighter markings. 
The washings contained a large proportion of Globigerina eretacea, 
Sphaeroidina bulloides also being found. 
This deposit seems originally to have been a blue mud, from 
the quantity of pyrites found infilling the foraminiferal shells and 
elsewhere, and from the small quantity of glauconite present. 
The depth determined by the foraminifera is 750 fathoms. 
Zone VI—This is a mottled blue-grey clay. There is much 
pyritous material as in Zone V. The deposit appears to be equiva- 
lent to the blue muds. 
The probable depth is 790 fathoms. 
Zone VII.—A dark blue-green clay, which from the scarcity of 
glauconite and the presence of pyrites, must have originally been a 
blue mud. This and the next zone above seems to have been formed 
under conditions particularly favourable for the existence of the 
redundantly grown Pulvinulina spinulifera. 
The depth for this zone is 810 fathoms. 
Zone VIII.—A grey clay, with a little glauconite in the fine 
washings. This also can be classed with the blue muds. The ferric 
carbonate casts become scarcer from Zone III. upward, and are 
entirely absent in this zone, so far as I have observed, but they 
again recur in the next and succeeding zones. 
