Rhoicosphenia species

Thomas, Evan W. & Kociolek, J. Patrick, 2015, Taxonomy of three new Rhoicosphenia (Bacillariophyta) species from California, USA, Phytotaxa 204 (1), pp. 1-21 : 15

Key to identify California Rhoicosphenia species and Rhoicosphenia abbreviata

1. Striae on both R- and D-valves are distinctly punctate......................................................................................................................2

- Striae on both R- and D-valves are not distinctly punctate................................................................................................................3

2. On raphe valves proximal raphe ends close together, less than 5 μm apart; valves oblanceolate, striae 9–11 in 10 μm on both valves ....................................................................................................................................................................................... R. lowei

- On raphe valves proximal raphe ends far apart, between 5–10 μm of separation............................................................ R. stoermeri

3. Valves linear-lanceolate, 3–6 μm wide, with narrow axial area and ovate central area................................................. R. californica

- Valves linear to narrowly clavate, 5–7 μm wide, with wide central and axial area tapering to valve apices ................ R. abbreviata