THE CRETACEOUS ROCKS OF BRITAIN. 
i74 
thick, and contains numerous green-coated nodules, which are 
feebly phosphatic. A special feature in its composition is the abund¬ 
ance of small fish-teeth and of minute pieces of bone ; it also contains 
glauconite in some quantity, but in small grains. The texture of 
the rock is coarser than that of the chalk above and below, while 
the nodules consist of fine-grained chalk-marl coloured and hardened 
by a slight infiltration of phosphate of lime. Where this “rag” 
occurs it separates the grey from the white chalk. 
The subzone of Actiiwcamax pleiius presents its usual Midland 
aspect, consisting of two layers of grey or bufi-coloured marl, with 
a course of firm, white, compact chalk between them, the whole 
being seldom more than 3 feet thick. 
Stiiatigiiaphical Details. 
Zone of Ammonites varians. 
Basement Bed. — At the base of this zone there is a soft glauco¬ 
nitic sandy marl like that in Berkshire, but so far as can be judged 
from the few exposures it is entirely without phosphatic nodules. 
No exposure of this “ Chloritic Marl ” was observed in Oxford¬ 
shire, but surface indications and ditch sections showed a complete 
passage upward from the soft Greensand at the top of the Sel- 
bornian to the soft Chalk Marl above, the amount of sandy and 
glauconitic material gradually decreasing upward, while that of 
chalky matter increases. 
The same conditions prevail in Buckinghamshire, and the actual 
passage from the “ Greensand ” through the glauconitic marl was 
seen by the roadside near Bushev Leys, south-west of Wendover, 
,and again by the main road about a mile north of Wendover. 
It was more clearly exposed in 1885 in a trench opened in the park 
near Aston Clinton House ; this showed about 6 feet of Chalk 
Marl at the upper end, passing down into glauconitic marl, and 
thence through marly greensand into a dark greensand consisting 
mainly of quartz and glauconite ; no line of division and no phos¬ 
phatic nodules existed, nor were any fossils observed. 
Chalk Marl. —There are many small exposures of the Chalk 
Marl in Oxfordshire, but none of any depth. 
The upper 18 feet of it were formerly seen below the Totternlw 
Stone at Crowmarsh (see 178), but this pit is now overgrown. 
There was also a small quarry by Bumbold s Lane, about 11 miles 
north of Hwelme, where about 5 feet of very hard chalk or marly 
limestone was seen in 1885, but Mr. Rhodes found it sloped and 
ploughed over in 1899. "From it I obtained Am. [Schl.] varians, 
Turrilites costatus , Inoceramus latus, Plicatula in ft at a, and Khyn- 
chonella gvasiana. I alsoobtained Am. [Acanth] Mantelli said other 
fossils from the material thrown out of a shallow well by Clay Lane, 
