Navicula Bory
	From the Latin navicula, "small ship"
For many years, the genus Navicula has included many species that simply did not fit into other genera. Recently, taxonomists have created new taxa to subdivide this very large, diverse genus using differences in morphology.	Navicula is a raphed, pennate diatom with boat-shaped cells that may exist singly or in ribbons. The valves are symmetrical both apically and transapically, and may have rounded, acute, or capitate ends. The central area is often distinctly expanded. The lineate striae are composed of elongated areolae arranged parallelly to the apical axis. However, the areolae may be difficult to see in many taxa, particularly in live, uncleaned samples.   Navicula is the largest diatom genus, with over 10,000 species, varieties, and forms. Navicula, like many other raphe-bearing diatoms, secretes mucilage from the raphe to enable the cells to glide along the substrate. In culture the cells may aggregate into irregular clumps.