Guide to Gomphonema californicum

Valves are lanceolate-clavate, with a rounded headpole and narrower footpole. The axial area is narrow and lanceolate. The central area rectangular and transversely extended. Striae are slightly radiate at the center, to strongly radiate toward the footpole; areolae distinct. Median striae on both sides of the central area are shorter. A single stigma is present. A characteristic feature is the presence of an apical spine at the headpole, which requires close examination in LM.