Foraminifera are a class of single celled amoeba. They are characterized both by their thin pseudopodia (feet) that form an external net for catching food, and they usually have an external shell. Most forams are aquatic, primarily marine, and the majority of species live on or within the seafloor sediment. For an excellent website describing forams from around the world, see: https://foraminifera.eu/index.html
From the Smithsonian Ocean: Microscopic, single-celled organisms called foraminifera have a fossil record that extends from today to more than 500 million years ago. Although each foram is just a single cell, they build complex shells around themselves from minerals in the seawater. These shells have accumulated in layers of sediment below the seafloor of the open ocean and in regions where the ocean once flooded the continents for millions of years. By examining the shell chemistry of these ancient forams, scientists can learn about Earth’s climate long before humans ever walked the planet—and get insight into how climate changed in the past.
This photograph was taken with a Galaxy S5 cell phone, hand held, through the eyepiece of one of the outreach Olympus BH-2 microscopes.