LOWER CHALK—NORTH WILTSHIRE. 
157 
conitic marl or chalk with scattered phosphatic nodules ; but of 
this there is only about 12 inches, and both the phosphates and 
fossils are much less abundant. 
Mr. W. Cunnington, who formerly resided at Devizes,- informed 
me that he obtained many fossils and phosphatic casts from a spot 
near the enclosed garden in Roundway Park. These fossils are now 
in the Museum of Practical Geology, and a list of them is given 
on ]). 163. It would appear that there must be a small patch of 
Chloritic Marl here resting on the plateau of the Upper Greensand. 
Another good exposure occurs on the road from Caine to Devizes, 
about half a mile west of Calstone. Here the Selbornian sands are 
directly succeeded by hard glauconitic marl, the base of which is 
piped into the sand. This glauconitic marl forms a solid bed 2J feet 
thick, and is crowded with phosphatic nodules and fossils ; above 
comes a second bed with fewer phosphates and less glauconite, 
which is about a foot thick, but passes up into Chalk Marl with 
still fewer green grains. Pecten asper occurs in the lower bed, but 
the shell is phosphatised and brittle. Terebratula biplicata, Tere- 
bratulina striata ,■ Rhynclionella grasiana , Pecten ( Neithea ) quinque- 
costatus, and Plicatula inflata occur with perfect calcareous shells. 
The glauconitic base of the Chalk is seen at Highway and Cleve- 
ancy, and still better in the cutting north of Chiseldon, on the 
Swindon and Marlborough Railway. My colleague Mr. Bennett 
furnishes the following note of this section: — “ At the north end of 
the cutting, and overlying some 25 feet of Greensand, the phos¬ 
phatic bed is seen dipping at about 7° southward. It is about 2 feet 
thick, the lower foot dark green with many phosphatic nodules; 
both green grains and nodules diminish in number upwards. Its 
base is marked by a line of reddish rusty material, probably from 
the decomposition of iron-pyrites.” 
Chalk of the Ammonites varians Zone. —Along the southern 
side of the Yale of Pewsey many of the deep-cut lanes which 
ascend the slope of the Chalk hills exhibit more or less continuous 
sections of the Lower Chalk. 
The lowest beds, immediately above the Chloritic Marl, are well 
exposed in the lane south of Urchfont, and consist of marly chalk 
with Am. [£c/U] varians and Am. [Acanthi] Mantelli, and higher 
up of whitish bloclyy chalk. 
The higher beds are also well shown in a lane ascending the escarp¬ 
ment south-east of Eastcott, and were described by Mr. Hill and 
myself in 1889A The lowest exposure here is between 120 and 130 
feet above the base of the Chalk, and is a small excavation showing 
abi ut 10 feet of whitish, flaggy chalk, which proved to contain 
much globular colloid silica. It also contains many of the siliceous 
nodules already mentioned, these occurring in a band of from 12 
to 18 inches in depth. At the top the chalk is greyish and harder, 
but still siliceous. 
* Quart. Journ. Geol. Soc., Vol. xlv. p. 405. 
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