MIDDLE CHALK—MICROSOPIC STRUCTURE. 5C^ 
The hard limestone from the top of the Cuvievi zone in Beer 
quarries is a true chalk, consisting of a fine chalk-paste crowded 
with shell-fragments, Foraminifera and Spheres, the fragments 
being of Echmodermal plates and spines, and of Inoceramus and 
Bracluopod shells. 
Examination of Residues. 
The results of ten analyses of the Chalk of this zone are given 
in the annexed table, no less than seven of them being from notes 
by Dr. Hume. Five of these are from an exceedingly interesting 
locality, viz., Beer in Devonshire, and they include the well- 
known Beer Stone. (See p. 513.) 
The amount of fine residue does not vary greatly, with the 
exception of the specimen from Eastbourne, which contains 7‘72 
per cent, of fine clay, an amount which exceeds that of many 
specimens at the summit of the zone of Holaster subglobosus. The 
next highest is that from the specimen from Beer, Devonshire, 
with 3'812 per cent. Those from Herts and Beds are much alike 
in character, while at Hessle we get for the first time a residue, 
of less than 1 per cent. The larger proportion of coarse residue, 
both in this and the Hitchin specimen, is accounted for by the 
occurrence of the small chaloedonic nodules. 
Detrital Minerals. — These occur in greatest variety in 
the Devonshire specimens. 
From the lower part of the zone at Beer Bay Dr. Hume identified 
Quartz, silvery white Muscovite and brown Biotite, and in the 
higher part of the zone Tourmaline is added to these. 
In the Beer Stone Dr. Hume recognises amongst the detrital 
minerals Quartz, Rutile, Tourmaline, Andalusite and Anatase. 
From other localities Quartz and Zircon are the only two which 
have been identified. 
The largest grains occur in the Beer Stone, one of them, slightly 
coloured yellow, having a diameter of '88 nun. The next largest is 
from our own specimen from Lulworth, the maximum here being 
*48 mm. The average size both at Beer and Lulworth is the 
same, viz., ‘15 mm. 
Secondary Minerals.— Glauconite was not found in any 
specimens from this zone, except in those from Devonshire. Deep 
green grains of glauconite are present in the Beer Stone, 
and small grains were scattered through the residue of an 
example from the bed which represents the Beer Stone in 
Beer cliffs. 
Dr. Hume records limonite in short, stout rods, consisting of 
small brown pellets bound together and changed externally into 
yellow oohre in many places. Irregularly shaped masses of iron 
oxide were of common occurrence in the more easterly 
specimen. 
