22 PROTOZOA—RHIZOPODA CLASS I 
mollusks, corals, bryozoans, coccoliths, radiolarians, diatoms, sponges, and 
Foraminifera. Of the latter, certain genera are remarkable for their extra- 
ordinary abundance (Globigerina, Orbulina, Pulvinulina, Biloculina), (Fig. 10). 
In the Atlantic and Pacific Oceans Globigerina ooze is the prevailing deep- 
sea deposit; in the North Sea, along the coast of Norway, Biloculina ooze. 
Numerous limestones and marls of older geological periods exhibit great 
similarity in structure and chemical composition to the now forming deep-sea 
oozes. White chalk (Fig. 11) is clearly a variety of abyssmal ooze, from which 
silicious constituents have become segregated out, and in which Teztularia 
predominate instead of Globigerina. Certain of the Eocene limestones of the 

Rie. 11 Thin slice of Planerkalk from Bohemia 
orig viewed in transmitted light under power 
Specimen of prepared white chalk from Meudon, as seen in of 50 diameters, showing sections of 
transmitted light under power of 300 diameters, showing Teztularia, Nodosaria, Rotalia, Frondicularia, and 
Globigerina, and Rotalia. numerous isolated Globigerina chambers. 
Paris basin are composed almost exclusively of the tests of Miliolidae, while 
others are made up of Alveolinae, and Nummulites. During the Carboniferous 
period the chief réle as rock-building organisms was played by Fusilina. 
Many dense, apparently homogeneous, or even semi-crystalline limestones of 
various ages, when examined microscopically in thin sections, are seen to be 
composed in large part of Foraminifera and other organic bodies (Fig. 12). 
Fossil Foraminifera are best preserved, being usually detachable from the 
matrix, and at the same time occur most abundantly, in unconsolidated marls and 
clays which are interbedded with calcareous strata, or in limestones of a chalky 
or earthy character. 
The tests of Foraminifera were first discovered by Janus Plancus, in 1730, 
on the beach of Rimini, and in the following year they were found by Beceari 
in the Pliocene of Bologna. They were long considered to be shells of 
mollusks, and were described by Breyn, Soldani, Fichtel, d’Orbigny, and 
others as Cephalopoda foraminifera, in distinction from Cephalopoda siphonifera. 
Dujardin, in 1835, was the first to recognise their true character as belonging 
to the Rhizopoda, 
