Silicoflagellates are single-celled flagellated protists that secrete a relatively simple siliceous skeleton generally less than 100 microns in length. Silicoflagellate skeletons have been recovered from many types of marine deposits and have been utilized by geologists in biostratigraphic and paleoecologic analysis. The systematics of this group is established upon overall skeletal morphology. Recently, the importance of ornamentation found on the surface of these skeletons has been emphasized The surface of the silicoflagellate skeletons may be smooth, or ornamented with spines, warts, linear striations, ridges and complex reticulations (i.e. ridges of silica in which at least three converge to a point on the skeleton).