FIGURES 98–104. Type material of Rhoicosphenia californica from Big Chico Creek, Butte County, California, USA. SEM. 98–101. External views of the R-valve show rounded puncta near the axial area and lineate puncta towards the margins (98, 100). At the head pole, the raphe continues onto the mantle and an open girdle band is visible (99). The central area has inflated proximal raphe ends (98, 100), and the foot pole has an apical pore field of rounded porelli (101). Internal views show the areolae through troughs between the virgae (102–104) and the proximal raphe ends are strongly crook-shaped in the same direction (103, 104). The valvocopula in modified to overlap the pseudosepta and an aperture is present in the valvocopula at the head pole (102, 104), but not at the foot pole (104). Scale bars are 5 μm (98) and 1 μm (99–104).