14 
THE CRETACEOUS ROCKS OF EMTAlX. 
.Marl.* This view, with other points, was the subject of contro 
versy at the time, but the differences of opinion were happily com¬ 
posed in 1894, when a joint note on the subject was written by Mr. 
Meyer and myself.f We pointed out that where the succession 
is most complete, as near Warminster and in the Isle of Wight, the 
.soft Greensand which contains the special Warminster fauna is 
succeeded by a glauconitic marl containing phosphatic nodules and 
the peculiar siliceous sponge Stauronema, Carteri (Sollas), but that 
in Dorset and Devon this Stauronema horizon does not occur. 
Hence, “ if the name Chloritic Marl is to be retained—and 
it seems to die hard—we think it should be restricted to the horizon 
or ‘ hemera ’ of Stauronema Carteri , and that the name should 
cease to be applied to the Scaphites bed of Dorset and Somerset, or 
to any bed in Devonshire .... We think that the War¬ 
minster Greensand and its equivalents should be regarded as the 
summit of the Upper Greensand, and the Stauronema bed or 
Chloritic Marl as the lowest horizon which can be included in 
the Chalk, this horizon being sometimes absent through non¬ 
deposition.” 
Still more recently the junction beds near Warminster have 
been minutely studied by Mr. J. Scanes and myself, with the 
result that between the Chert Beds of the Selbornian and the 
Chloritic Marl with Stauronema we distinguish three separate 
layers and find that all the characteristic fossils of the Chloritic 
Marl, except Stauronema , range down through two of these 
layers. But whether these two layers should be included in the 
Chalk or in the Selbornian was left an open question.J We now 
think that they should be taken into the zone of Am. varians and 
regarded as the base of the Chalk. 
Another deposit which has been called both Upper Greensand 
and Chloritic Marl is that which is more correctly known as the 
Cambridge Greensand. This is a dark sandy glauconitic marl, full 
of black phosphatic nodules and phosphatised fossils, which forms 
a constant bed at the base of the Chalk Marl along its outcrop in the 
counties of Bedford, Hertford, Cambridge, and Suffolk, resting 
directly upon an eroded surface of the Gault. 
Up to 1875 the Cambridge Greensand was generally regarded 
as a thin local representative of the Upper Greensand, because it 
was supposed that the Gault was always succeeded by Upper 
Greensand. In 1872 Professor Bonney read a paper in which he 
correctly described the bed as occurring at the bottom of the Chalk, 
and as resting on an eroded surface of the Gault, and he regarded 
the nodules it contains as derived from the Gault: nevertheless he 
still considered the bed to be “the equivalent of the Upper Green- 
* On the Cretaceous Bocks of Beer Head. Quart. Journ. Geol. Soc., 
Vol. xxx. p. 381. See also Geol. Mag., Dec. ii. Vol. v. p. 547 (1878). * 
t Geol. Mag., Dec. iv. Vol. i. p. 494. 
£ Quart. Journ. Geol. Soc. Vol. lvii. p. 124. U— 
