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Updated: June 23, 2025
The Globigerinoe, Cyatholiths, Coccospheres, Discoliths in the one are absolutely identical with those in the other; there are identical, or closely analogous, species of Sponges, Echinoderms, and Brachiopods.
That this precipitation takes place all over the area where the icebergs are breaking up, constantly, and to a considerable extent, is evident from the fact of the soundings being entirely composed of such deposits; for the Diatoms, Globigerinoe, and radiolarians are present on the surface in large numbers; and unless the deposit from the ice were abundant it would soon be covered and masked by a layer of the exuvia of surface organisms."
In favour of this view, it has been urged that the shells of the Globigerinoe of the surface never possess such thick walls as those which are fouled at the bottom, but I confess that I doubt the accuracy of this statement. Again, the occurrence of minute Globigerinoe in all stages of development, at the greatest depths, is brought forward as evidence that they live in situ.
Nor can the presence of the soft parts of the body in the shells which form the Globigerina ooze, and the fact, if it be one, that animals living at the bottom use them as food, be considered as conclusive evidence that the Globigerinoe live at the bottom.
Carpenter, and Professor Wyville Thomson, in their earlier cruises; and the continuation of the Globigerina ooze over the South Pacific has been proved by the recent work of the Challenger, by which it is also shown, for the first time, that, in passing from the equator to high southern latitudes, the number and variety of the Foraminifera diminishes, and even the Globigerinoe become dwarfed.
Then the young Crania adhered to the bared shell, grew and perished in its turn; after which, the upper valve was separated from the lower, before the Echinus became enveloped in chalky mud." A specimen in the Museum of Practical Geology, in London, still further prolongs the period which must have elapsed between the death of the sea- urchin, and its burial by the Globigerinoe.
Another consideration appears to me to be in favour of the view that the Globigerinoe and their allies are essentially surface animals. This is the fact brought out by the Challenger's work, that they have a southern limit of distribution, which can hardly depend upon anything but the temperature of the surface water.
I say substantially, because there are a good many minor differences; but as these have no bearing on the question immediately before us, which is the nature of the Globigerinoe of the chalk, it is unnecessary to speak of them. Globigerinoe of every size, from the smallest to the largest, are associated together in the Atlantic mud, and the chambers of many are filled by a soft animal matter.
In working over the soundings collected by Captain Dayman, I was surprised to find that many of what I have called the "granules" of that mud were not, as one might have been tempted to think at first, the more powder and waste of Globigerinoe, but that they had a definite form and size. I termed these bodies "coccoliths," and doubted their organic nature. Dr.
If, on the other hand, it is to be used as a mineralogical term, I do not see how the modern and the ancient chalks are to be separated and, looking at the matter geographically, I see no reason to doubt that a boring rod driven from the surface of the mud which forms the floor of the mid-Atlantic would pass through one continuous mass of Globigerina mud, first of modern, then of tertiary, and then of mesozoic date; the "chalks" of different depths and ages being distinguished merely by the different forms of other organisms associated with the Globigerinoe.
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