FIGURES 1–18 in Planothidium sheathii a new monoraphid diatom species from rivers in California, USA

FIGURES 1–18. Planothidium sheathii LM views. Figs 1, 2, 5–9, 11–18 are SV. Figs 3, 4, 10 are RV. The same valve is presented at different focal plane to show the cavum hood aperture on figures 5 and 6, 11 and 12, 13 and 14, 15 and 16, 17 and 18. Figs 8, 9 and 10 are the same frustule. Arrows show cavum hood aperture borders fusion with neighboring virga on SV, arrowheads show more distant central shortened striae on RV. Figs 1–16 from the type locality San Joaquin River. Fig. 7 represents the holotype. Figs 17, 18 from Merced River, California, USA. All scale bars: 5 μm.