Introduction .—The Mediterranean has been the source whence a large number of the known species of Foraminifera have been derived. Beccarius (1731), Plancus (Bianchi, 1739), Gualtieri (1742), Ginanni (1755), Soldani (1780 & 1789), and Fichtel and Moll derived most of the material for their notices of these microscopic shells from the Mediterranean. D’Orbigny also and later naturalists have drawn largely from this rich source. Of late years, we have been favoured with the results of many dredgings taken in different parts of the Mediterranean by Prof. E. Forbes and Capt. E. Spratt, also with shell-sands from Leghorn and Venice by Mr. W. J. Hamilton, and with other shell-sands from both sides of Italy by Prof. Meneghini and the Marchese Carlo Strozzi (through the zealous kindness of Dr. H. Falconer), with sponge-sands from Crete and elsewhere (communicated by friends), and we have obtained other like material from various sources. We have thus been able to work out a very large series of the Mediterranean Foraminifera . The authors already mentioned, as well as Defrance and others, have also described a large number of fossil Foraminifera , obtained from the Tertiary deposits of Tuscany, Piedmont, and other countries bordering the Mediterranean. These bear a close relation to the recent forms of the same area; and towards the elucidation of their affinities, we can now bring forward the results of a careful examination of an extensive series of the fossil Foraminifera of the Mediterranean region, either supplied to us by some of the friendly hands above