428 
DR. G. J. H1NDE ON BEDS OF SPONGE-REMAINS IN THE 
fine powder from the cavities in the chert of Warminster, and in the powder which 
may be obtained with a needle from fractured surfaces of the friable portions of the 
malm of Merstham or Farnham. When this powder is mounted in water or in Canada 
balsam, it is seen under the microscope largely to consist of the globular bodies, either 
single and cpiite free (Plate 45, figs, 18, 19, 19c/), or in groups of two, or three, or 
several individuals united together (Plate 45, figs. 18a, b, 19a, b, c). The single 
globules present well-defined circular outlines ; the individuals forming the groups are 
also circular, except where in contact they partially coalesce, and their margins 
beoome abruptly truncated. In some instances the globules are ranged in a linear 
series, in which the individual components are only indicated by slight lateral inden¬ 
tations. Frequently these bodies ar'e clustered round the residuary spicules and 
attached to the solidified canals of spicules, whose walls have been dissolved away 
(Plate 45, fig. 16). In the malm of Farnham the globules in some instances are aggre¬ 
gated into larger spherical bodies. 
These globules, when magnified about 500 diameters, present well-marked varia¬ 
tions. In the commonest forms there is a marginal ring, about one-sixth the diameter 
of the globule, which seems to be faintly striate, whilst the central portion has a 
granular appearance (Plate 45, fig, 18). In another form the surface is covered with 
faint striae which radiate from an indefinite central granule (Plate 45, fig. 19 d). In 
another form, which is nearly entirely confined to the fine material from the War¬ 
minster chert, there is a central well-marked circular area, from one-third to one-fifth 
the diameter of the globule (Plate 45, figs. 19, a, b, c ). This central area is usually 
furnished with an ill-defined nuclear spot, and its margins are lighter than the outer 
portion of the globule, which is radiately striated. The strife or rays are, in all cases, 
of a very faint character, and distinguishable only in the best preserved examples. 
The very smallest and simplest globules consist of perfectly clear silica without stria? 
or granules. 
It is somewhat difficult to ascertain with precision the true form of these minute 
bodies. Some are certainly plano-convex discs, others are biconvex, and the smaller 
bodies may approach a spherical form. 
The globules are very variable in size ; the smallest forms are only ’0014 mm. in 
diameter, and from this there are all gradations of size to bodies of *045 mm. in width, 
or more than thirty times the diameter of the smaller. The majority of them vary 
between ‘013 and '02 mm. in width. 
By transmitted light the globules are translucent, and present the same pinkish 
tint as the colloidal silica of the spicules ; by reflected light they have also the same 
bluish-white or opal aspect as the spicules. They are negative between crossed 
nicols, when freed from particles of calcite, which are often present, in the same 
deposits. They also readily dissolve -when treated with caustic potash, 
In the soft, friable beds of malm, the siliceous globules, which frequently constitute 
a large proportion of its mass, are mostly free, or but lightly consolidated together by 
