Silicoflagellidae

a family of protozoans of the order Chrysomonadina, class Mastigophora. They are marine forms with one flagellum and yellow chromatophores. The silica skeleton is shaped like a ring or a latticed basket. Silicoflagellidae make up dwarf plankton (nannoplankton); their dimensions are less than 50 microns. They are sometimes found in large numbers. Their skeletons are well preserved in the fossil state and serve as index fossils in stratigraphy.