PROTOZOA 



2/ 



tiful. They may consist of a single chamber as in the spherical 

 Orbulina, which possesses numerous fine pores and one large 

 opening; or there may be several or even a large number of 

 chambers, connecting with one another but joined in the 

 most varied fashion, end to end, side by side, in a spiral, 

 a helix, and so on (Fig. 6). It is these shells which are so 

 abundant at the bottom of the ocean, where they constitute a 

 conspicuous layer known as Globigerina ooze, because of the 

 large number of Globigerina shells (Fig. 6) which it contains. 



psd 



ophldkhhryi 



FlG. 7. A Heliozoon. c.vac, contractile vacuole; nu, nucleus; psd, 

 pseudopodia ; sp, skeletal spicules. (From Butschli's Protozoa.) 



These calcareous shells are also abundant as fossils and in fact 

 constitute about three fourths of all the fossil Protozoa. The 

 chalk formations of Europe contain many species, and the 

 Nummulitic limestone of the Pyrenees is composed largely of 

 various kinds of Nummulites (Fig. 6), having a flat, disklike 

 shell with complicated, spirally arranged chambers ; these 

 shells may have a diameter of five or six centimeters. In the 

 United States, formations containing Foraminifera are very 

 abundant in South Carolina, Virginia, and many other states. 



