An order of Lobosia. The shell (test) of these protozoa has a single, well-defined aperture through which slender fingerlike pseudopodia (lobopodia) can be extended. The test often has an internal chitinous layer known as a glycocalyx and an external layer composed of secreted siliceous elements, organic hollow platelets, or collected sand grains and other matter cemented together by an adhesive secretion. The secreted platelets are synthesized within membranous vesicles in the cytoplasm, where they first appear as dense granules. These granules are transported to the surface of the cell, where they are deposited on the outer surface of the cell membrane and mature into the alveolate, closely assembled platelets.