The answer is phylum Sarcodina and class Heliozoa.
Actionophryx belongs to the group of amoebas, in older classification known as phylum Sarcodina. It has a spherical body with axopodia (arms) so it is classified to the class Heliozoa. The body is surrounded by a glassy silica shell. It lives in freshwater, but some species are found in seas and oceans.