MIDDLE CHALK—MICROSCOPIC STRUCTURE. 501 
In notes on the white chalk of Yorkshire, by Major-General 
Emmett,* Messrs. Parker and Jones suggest that these minute 
chambers were “ separate cells of Globigerina and Dentalina , the 
former predominating.” 
M. Cayeux, who has also noted their extreme abundance in the 
chalk, particularly at the base of the Turonian, in many localities 
in the Paris basin, refers to them as monoloeular Foraminiferat 
of the genus Fissurina or Orbulina. In the zone of Inoceramus 
labiatus near Bouen, he estimates the Spheres to form 95 to 
98 per cent, of all the Rhizopodal fauna (pages 288 and 305j. 
In 1890 Dr. Hinde wrote : “ I do not think they can be placed 
with Radiolaria, and they are not to be included with sponges.”! 
Mr. F. Chapman, who also kindly examined some of our wash¬ 
ings containing Spheres, believed some of them to be Badiolaria, 
and thought that in some instances he could make out a “ medul¬ 
lary cell ” and its supports, and see also traces of the siliceous 
network of the walls. In other more flattened sphseroids, he saw 
a strong resemblance to the globate dermal spicules of certain 
sponges; but the real nature of the majority of these calcareous 
spheres still remains an enigma. 
Besides the Spheres, there occur in most chalks many i! cells ” 
which, without doubt, are the young of Foraminifera, and are not 
infrequently double. Though single cells can easily be con¬ 
founded with true Spheres, they may usually be recognised by 
their thinner walls and by some irregularity of outline. Such 
cells are more easily recognised in the Upper Chalk, where they 
sometimes form the most prominent feature in thin sections, and 
where Spheres artless abundant. 
In all specimens examined from Dorsetshire the nodules are 
ill-defined, and the rock consists chiefly of spheres thickly packed 
in a calcareous paste, now indurated by. semi-crystalline granular 
calcite, while here and there large Globigerina and a few Textu - 
(aria occur. Large, coarse shell-fragments are not common, but 
the matrix of several specimens is full of minute calcitic particles 
probably derived from shells. 
Specimens of Melbourn Bock from Wiltshire and from all counties 
to the north-eastward, including Suffolk and Norfolk, and those 
also from the south-eastern counties including Hampshire and the 
Isle of Wight, all present much the same general characters. 
The leading feature in all cases is the abundance of shell-frag¬ 
ments, either fine or coarse, and of Spheres. The shell-fragments 
* Geologist, Vol. iii., p. 420, 1860. 
t Contribution k l’Etude Micrographique des Terrains Sedimentaires, 
pp. 222, 263, 267, 401, etc. 
X Joum. Boy. Mic. Soc., 1890. 
4219. 
K K 
o 
