Caloneis Guide
Credit: Sarah Spaulding
  1. Striae chambered
  2. One or two longitudinal lines may be present
  3. Central area may have irregular thickened areas

Species of Caloneis are characterized by chambered striae, like those of Pinnularia. The chambered striae give the appearance of one to two longitudinal lines. The striae of Caloneis are composed of fine alveoli, also like Pinnularia. The central area of Caloneis may be expanded, and may include silica thickenings that are lunate or irregular in shape. Living cells possess one or two plastids.

Several species within Caloneis are common in North America in alkaline, brackish and marine habitats. Several taxonomists suggest that Caloneis is a synonym of the closely related genus Pinnularia and that the two genera should be combined into a single genus.