Foraminifera are members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm that among other things is used for catching food, and commonly by an external shell or "test" made of various materials and constructed in diverse forms. All but perhaps a very few are aquatic and most are marine, the majority of which live on or within the seafloor sediment while a smaller variety are floaters in the water column at various depths. A few are known from freshwater or brackish conditions and some soil species have been identified through molecular analysis of small subunit ribosomal DNA.