Fig. 8. — Forms of Life that contribute to the Organic Deposits in Deep Oceansa, Holtenia carpenteri, Wyville Thomson, a siliceous sponge, the spicules of which go to form the flint nodules in chalk and the bands of chert in dolomite, b, Pentacrinus wyville-thomsoni, Jeffreys, a crinoid that yields calcium carbonate to the sediments, c, Globiyerina bulloides, d'Orbigny, highly magnified. The dead shells are shown as they fall to the bottom of the sea. d, Coccosphere, made of coccoliths very highly magnified, c and d are free-swimming organisms that yield the greater amount of calcareous matter to the deep sea oozes which consolidate as chalk. (From Professor Wyville Thomson's Depths of the Sea, Macmillan & Co.)
49
