278 
THE CRETACEOUS ROCKS OF BRITAIN 
Mineral grains are more abundant in South Dorset than in 
North Dorset. Glauconite is always present in smallish grains, 
which are more abundant in the lower than in the higher beds. 
Sponge-spicules, thin and threadlike, are seen most commonly in 
the [hard lumps which occur all through the Am. varians zone of this 
county. The specimen 20 feet above the top of the Chloritic Marl, 
Mupe Bay (10), may be taken as a type. In this “ spheres ” are very 
numerous, and occupy about 40 per cent of the area of the section, 
shell-fragments make about 10 per cent. Glauconite occurs in excep¬ 
tionally large grains, and these, with fragments of quartz, show in 
strong relief. The area occupied by Poraminifera is insignificant. 
Sponge-spicules do not occur in this specimen. 
The specimen fromDogbury Hill (Cerne, North Dorset), 6J feet 
above the Chloritic Marl, (11) differs little from the above, except 
in the amount of mineral grains and glauconite, the former being 
comparatively rare, while the latter are much smaller. 
Isle of Wight.— The lower beds of this zone in the Isle of Wight 
are crowded with shell-fragments. (See Plate IV., Pig. 1.) In a 
specimen from 10 feet above the Chloritic Marl at Compton 
Bay (12) they may be estimated at 50 per cent, of the rock. 
Spheres are common; grains of glauconite are rather large and 
conspicuous, though widely separated. Mineral grains are not 
abundant. Sponge-spicules are present, but are not of frequent 
occurrence. There are more Poraminifera to be seen than in 
Dorset specimens, but they form a very small part of the rock ; 
they appear to be chiefly arenaceous forms. One or two 
Textularia can be recognised, but Globigerina is rare. 
At Culver Cliff, 10 feet above the Chloritic Marl, shell-fragments 
are still more abundant, and form about 75 per cent, of the rock. 
The fragments are nearly all prisms of Inoceramus, and appear to 
have been rolled. Glauconite is abundant, estimated at 10 per 
cent., mineral grains rare, “ spheres ” seem crowded out, a few 
large Poraminifera, and here and there a sponge-spicule occurs. 
A specimen from the upper part of this zone at Culver Cliff 
presents a strange contrast: it contains scarcely a single shell- 
fragment, and, with one exception, such as do occur are minute. 
“ Spheres,” on the other hand, are abundant, and form at least 
half the rock. There are a few minute grains of glauconite widely 
separated, but not a mineral grain is discernible. Sponge-spicules 
are not visible in the sections examined, but occur in the residues. 
Sussex and Kent.—A specimen from the upper part of the zcne 
at Eastbourne shows the rock to be very full of “ spheres,” with a 
few large Globigerince, but scarcely any shell-fragments. 
In the specimen from East Wear Bay, near Do\er, 10 feet above 
the Chloritic Maid (15), shell-fragments of irregular size form 
perhaps 20 per cent, of the deposit; mineral grains are common, 
scattered irregularly through the mass. “ Spheres ” seem absent, 
and few Foraminifera other than arenaceous forms, whose outline 
