508 
Proceedings of the Royal Society 
muds. The remains of calcareous organisms are at times quite 
absent, but occasionally they form over 50 per cent. The latter is 
the case when the specimen is taken at a considerable distance from 
the coast and at a moderate depth. These calcareous fragments 
consist of bottom-living and pelagic Foraminifera, Molluscs, Polyzoa, 
Serpulse, Echinoderms, Alcyonarian-spicules, Corals, &c. The re- 
mains of Diatoms and Eadiolarians are usually present. Generally 
speaking, as we approach the shore the pelagic organisms disappear ; 
and on the contrary, as we proceed seawards, the size of the mineral 
grains diminishes, and the remains of shore and coast organisms give 
place to pelagic ones, till finally a blue mud passes into a true deep- 
sea deposit. In those regions of the ocean affected with floating ice 
the colour of these deposits becomes gray rather than blue at great 
distances from land, and is further modified by the presence of a 
greater or less abundance of glaciated blocks and fragments of 
quartz. 
Green Muds and Sands . — As regards their origin, composition, 
and distribution near the shores of continental land, these muds 
and sands resemble the blue muds. They are largely com- 
posed of argillaceous matter and mineral particles of the same 
size and nature as in the blue muds. Their chief character- 
istic is the presence of a considerable quantity of glauconitic 
grains, either isolated or united into concretions. In the latter case 
the grains are cemented together by a brown argillaceous matter, 
and include, besides quartz, felspars, phosphate of lime, and other 
minerals, more or less altered. The Foraminifera and fragments of 
Echinoderms and other organisms in these muds are frequently 
filled with glauconitic substance, and beautiful casts of these 
organisms remain after treatment with weak acid. At times there 
are few calcareous organisms in these deposits, and at other times 
the remains of Diatoms and Eadiolarians are abundant. When these 
muds are dried they become earthy and of a grey-green colour. 
They frequently give out a sulphuretted hydrogen odour. The 
green colour appears sometimes to be due to the presence of organic 
matter, probably of vegetable origin, and to the reduction of peroxide 
of iron to protoxide under its influence. The green sands differ from 
the muds only in the comparative absence of the argillaceous and 
other amorphous matter, and by the more important part played by 
