MIDDLE CHALK—MICROSCOPIC STRUCTURE. 519 
We append the notes writen by Dr. Hume on the residue of 
the sample from Beer which was analysed by him. 
“ Terebratulina Zone (half-way up Beer Clift).—This zone 
yielded a considerable residue ; the part coarse enough to be 
examined weighed *077 grammes and consisted largely of clial- 
cedonic aggregates, limonite, a large number of minute glob¬ 
ular casts of Foraminifera, sometimes still united, and showing 
to have been formed in the tests of the delicate species 
Textularm globulosa. Glauconitic rods are abundant, while 
flakes of muscovite and biotite form an important element. 
Quartz is represented by three or four larger fragments '4 mm. 
in diameter, a fine quartzose residue being practically absent. ‘038 
grammes of the residue consists of the chalcedonic meshes pre¬ 
viously referred to. 
“The finer material consists of—(1) Yellow ochre and red aggrega¬ 
tions of limonite, which break up easily when submitted to light 
pressure. One piece is covered with minute botryoidal projections. 
(2) Foraminiferal tests which have undergone extreme chalce- 
donification. The most striking objects in this respect were forms 
which have been probably derived from some form of Nodosaria. 
The chambers have become somewhat distorted, but their indi¬ 
viduality is still marked, and the final chamber of the series termi¬ 
nates in a pointed extremity, such as is common in many species 
of Nodosaria. On being touched with a brush these immediately 
broke to pieces. (3) Light yellow glauconitic casts of Foramini¬ 
fera are abundant, the largest of these, expanded into a large tri¬ 
angular chamber after the manner of Cristellaria , is ‘166 mm. in 
length, but the majority of the rounded single chambers are about 
*08 mm. diameter. In addition to these occur spheres joined 
together by stoloniferous connections, these presenting several 
varieties. In one case three are connected together, one being in 
a different plane from the other two ; again, there are irregular 
aggregations of five or more chambers, as in some Globig evince , 
and, lastly, there is the regular arrangement of alternating foli- 
aceous chambers on two sides of a central axis, as in Textularia. 
Some of these glauconite grains are still inclosed in the silicified 
tests. (4) In addition, there are glauconite rods, some 4 mm. in 
length, none showing any terminal projection or ornamentation, 
but which, nevertheless, from analogy are probably the internal 
casts of sponge-spicules. (5 ) Muscovite and biotite mica flakes 
of small size are present, but no heavier minerals have been 
observed. 
“ This zone, therefore, shows a considerable diminution in the 
detrital materials present, and also begins to show evidence of the 
presence of sponge spicules which play such an important part in 
the zone of Holaster planus . A noticeable feature is the exceed- 
ingly small amount of quartz in the residue.” 
W. F. Hume. 
