Lower chalk— micrograrhic structure. 321 
very rare, all of those found were Trochammina concava , except 
a single specimen of Pleurostomella alternans. A few shell-frag¬ 
ments, chiefly Inoceramus- prisms, occurred, and one or two pieces 
apparently fish-scales. There were also two grains of glauconite ; 
this mineral did not occur in the acid residue. 
The finest material, though containing a large percentage of cal¬ 
careous particles, contained also much inorganic matter. This was 
in the form of fine clay, but in it were many minute mineral par¬ 
ticles too small for identification, but which give a decided reaction 
with polarised light. Minute opaque particles abounded, and 
there were also many minute opaque masses of irregular yet more 
or less globular form. Tew of these exceed * 01 mm. in diameter, 
which precludes the idea that they may be “ spheres ” infilled with 
opaque material. 
The calcareous particles were chiefly minute ealcitic crystals 
giving no clue to their derivation. Larger particles, probably derived 
from shells or from Toraminifera and crystalloids, were far less 
abundant than in Southern specimens. 
Cerne Abbas. —Toraminifera were fairly common in this speci¬ 
men, but they were very small, and many minute Textularia and 
Globigerina came away with the finer parts of the marl when 
washed. None were isolated. The coarsest particles consisted chiefly 
of Inoceramus -prisms broken into small pieces and a few valves of 
Ostracoda , and one or two broken Echinoderm spines. 
The finest material seemed to consist largely of calcitic particles, 
and crystalloids were common though hardly abundant. The 
inorganic material was an extremely fine clay with a few minute 
mineral particles. 
Hitchin (lower band).—This contained a good many Toramini¬ 
fera and Ostracod valves. There were also several minute and 
broken Echinoderm spines, and the ossicles of a starfish were 
also common. No large shell-fragments occurred amongst the 
coarser particles, the whole being much broken up. The amor¬ 
phous matter consisted largely of minute calcitic particles, amongst 
which crystalloids were abundant. 
Dover.— In the Dover marl Toraminifera are still more abundant, 
and several species of Ostracods occurred. The coarsest calcareous 
particles included plates and spines of Echinoderms, calcareous 
bodies of peculiar character which are probably ossicles of star¬ 
fish (see page 510), a few flat shell-fragments, and portions of what 
appeared to be a Rhynclionella and Inoceramus prisms. Two or 
three minute fish-teeth, ovoid coprolites, and some pieces of scales 
were also found. Although there is considerable diversity in these 
coarser particles the actual amount of them is not large. 
In the finest washings small Toraminifera were very common, 
consisting chiefly of small Globigerina, Textularia and “ spheres ” ; 
crystalloids are also abundant. 
