The theca is elongate, tubular, often slightly curved and irregu−
larly shaped. The apertural (proximal) end is usually
wider and more broadly rounded compared to the narrower apical (distal) end. The aperture is single, terminal, small and rounded. It may project slightly but
is sometimes retracted and invisible. The cytoplasm is white to yellowish, dense and fluffy with fine granules. It
fills the theca almost entirely, sometimes leaving small empty spaces at both ends.
Elongate organic test withtransparent reflective wall. The cell body is white and transparent with fine granules and numerous mineral particles, which are concentrated at the apertural end. A great majority of the mineral particles consist of magnetite and titanoferous magnetite.