THE VOYAGE OF H.M.S. CHALLENGER. 
:}94 
ill the Green Sand from 100 and 150 fathoms. In the deep-water specimens there 
is an abundance of calcareous organic remains, especially Khizopods, a diminution of 
mineral particles, and a great preponderance of phosphatic matter. The phosphate 
penetrates the sliells in every part, and pseudomorphoses them in a more or less complete 
manner. It also forms large patches, enclosing organisms and minute mineral particles, 
which do not show structure, properly speaking ; they are slightly brownish with 
transmitted light, and appear to occupy the place of the muddy calcareous matter 
usually found between the Foraminiferous shells in a Globigerina Ooze. These phos- 
phatic patches are characterised by a certain opacity due to the inclusion of a crowd of 
infinitesimal heterogeneous particles. It might be said that the phosphatic matter, 
when infiltrating into the mud, had embraced and cemented all the immediately sur- 
rounding impurities. Although, as already stated, these patches present no structure, 
they are lined by a zone which resembles in character concretionary phosphate of lime 
(see PI. XX. fig. 4). It might be suggested that the fundamental mass in solidifying 
had concentrated the organic and mineral matters of the deposit, and in so doing had 
left behind microscopical empty spaces, which had subsequently been fiilled by infiltra- 
tions of a more homogeneous phosphate of lime, and that this was deposited in these 
cavities in a manner resembling substances coating some geodes. These later additions 
of phosphate of lime, being of purer matter, more transparent, slightly yellowish, have 
solidified with the curvilinear contours and fibro-radiate structure of some concretionary 
coatings. Between crossed nicols the fundamental mass of these sections can be seen 
to remain without sensible action on polarised light, while the zone surrounding the 
borders reacts in giving a rather vivid tint. In the same way the external parts of the 
concretions offer in thin sections a border of transparent phosphate without inclusions, 
and with concretionary structure, as if the later depositions had been formed of a more 
homogeneous material (see PI. XX. figs. 3 and 4). The same observation is applicable 
likewise to the infiltrations into the hollow spaces of the microscopic Foraminifera shells. 
In these tliin sections the Foraminifera that have been aggregated by the phosphate 
are sharjily distinguislied from it by the colourless calcareous matter of their shells. 
Tlie interior formerly occupied by the sarcode is filled by a honey-coloured phosphate, 
the pho.sphate infiltrated by the foramina of the PJiizopods being much purer than that 
cementing the particles of the deposit ; but this deposition of phosphate in the interior 
of the calcareous shells has sometimes been accompanied by brownish pigmentary 
matters, which arc evidently hydrated oxide of iron associated with organic matters 
(see PI. XX. fig. 2). The interiors of the Rhizopods in this way appear generally like 
yellowish, or in some cases like little black, mas.ses limited by the calcareous enveloi)C of 
the shell. 
The infiltration of })hosphate is not always limited to the filling up of the 
cavities of Foraminifera and other organisms ; a pseudomorphic substitution of the 
