Phylum Sarcodina

These ciliates have a most unusual way of getting about. They extend part their body in a certain direction, forming a pseudopod or false foot, and then flow into that extension (cytoplasmic streaming). Many forms have a tiny shell made from organic or inorganic material. They eat other protozoans, algae, and even tiny critters like rotifers. Amoeba is a typical member of this phylum. Many sarcodines are parasites, such as the species Entamoeba histolytica, which causes amoebic dysentery. 10 million Americans are infected at any one time with some form of parasitic amoeba, and up to half of the population in tropical countries. Somewhat more unusual sarcodines are the Foraminiferans. These "forams" can have fantastically sculptured shells, with prominent spines. They extend cytoplasmic "podia" out along these spines, which function in feeding and in swimming. Forams are so abundant in the fossil record, and have such distinctive shapes, that they are widely used by geologists as markers to identify different layers of rock. The famous white cliffs of Dover are made up of billions of foraminiferan shells.