An unornamented, thicked rib of silica located between fascicles. Usually applied to centric diatoms.
Fissure that joins the proximal raphe ends in some cymbelloid taxa. Instead of distinct terminations, the proximal raphe ends are connected internally by a fissure.
A valve with poles, or apices, of the apical axis having the same size and shape. Isopolar valves are symmetrical to the transapical axis.
A specimen from the original collection of the holotype and of the same taxon. A type material recognized by the International Code of Nomenclature for algae, fungi and plants (ICN).