Lanceolate refers to a "leaf shape" and may range from wide to narrow or fusiform.
Silica extension of the cingulum; in some taxa, projects to intersect with neighboring girdle bands.
Lineolae are areolae that are transapically elongated and are characteristic of Navicula sensu stricto, or Navicula in the Lineolate group.
In the genus Aulacoseira, linking spines join frustules together in a chain, or filament.
Light microscopy is abbreviated by 'LM'. The study of diatoms relies on a compound microscope in which a beam of light passes through optical lenses to view an image of the specimen. Contributors to the Diatoms of the United States project use research grade microscopes with the minimum specifications of 100x, 1.3 numerical aperature (NA) oil immersion objective lens and 1.3 NA condenser lens.
Valve walls that have more than one layer of silica may have a complex, chambered structure. Areolae may also be considered to be chambered, or loculate (the chamber is termed the loculus)
A canal positioned between the primary and secondary layer of silica. Longitudinal canals may be central or marginal and are found in some genera, including Neidium and Muelleria.
The longitudinal rib is a solid silica structure that runs along the apical axis.
The term, lunate, refers to a moon, or crescent, shaped structure. The term is used to describe a thickened silica shape in the genus Caloneis.