But it is to the Tertiary formation that these zoophytes have contributed the most enormous deposits. The greater part of the Egyptian pyramids is only an aggregation of _Nummulites_ inserted in the syenite. A prodigious number of Foraminifera present themselves in the tertiary deposits of the Gironde, of Italy, and of Austria. The chalk so abundant in the basin of Paris is almost entirely composed of Foraminifera. The remains of these creatures are so abundant in the Paris chalk, that M. d'Orbigny found upwards of fifty-eight thousand in a small block, scarcely exceeding a cubic inch of chalk, from the quarries of Chantilly. This fact, according to this author, implies the existence of three thousand millions of these zoophytes in the cubic mètre (thirty-nine inches square and a small fraction) of rock! As the chalk from these quarries has served to build Paris, as well as the towns and villages of the neighbouring departments, it may be said that Paris, and other great centres of population which surround it, are built with the shells of these microscopic animals. The sand of the littoral of all existing seas is so full of these minute but elegant shells, that it is often half composed of them. Ehrenberg, the celebrated German microscopist, was recently invited by the Prussian government to assist in tracing the robbery of a special case of wine. It had been repacked in littoral sand only found in an ancient sea-board in Germany. The criminal was thus detected. M. d'Orbigny found in three grammes (forty-six grains troy) of sand from the Antilles, four hundred and forty thousand shells of Foraminifera. Bianchi found in thirty grammes (four hundred and sixty-seven grains) from the Adriatic, six thousand of these shells. If we calculate the proportion of these beings contained in a cubic mètre alone of sea-sand, we reach a figure which passes all conception. What would this be if we could extend the calculation to the immensity of surface covered by the waves which surround the globe? M. d'Orbigny has satisfied himself, by microscopic examination of sands from all parts of the globe, that it is the débris of Foraminifera which form, in all existing seas, those enormous deposits which raise banks, obstruct the navigation in gulfs and straits, and fill up ports, as may be seen in the port of Alexandria. In common with the corals and madrepores, the Foraminifera are the great agents in forming the isles which surge up under our eyes from the bosom of the ocean in the warmer regions of the globe. Thus shells, scarcely appreciable to the sight, suffice by their accumulations to fill up seas, while performing a very considerable part in the great operations of Nature, although it may not be apparent to us.