FIGURES 105–110. Type material of Rhoicosphenia californica from Big Chico Creek, Butte County, California, USA. SEM. 105–108. External views of the D-valve show the shortened raphe branches and round to lineolate areolae (105). The distal raphe end at the head pole terminates on the valve face (106) and continues onto the mantle at the foot pole (107). The proximal raphe end at the head pole is small (106) and at the foot pole is dilated (107). In girdle view, the foot pole can be seen on each valve along with a single row of simple poroids on the valvocopula (108). Internal views show the external areolae through troughs between the virgae (109). Pseudosepta are covered at each pole by the valvocopula and the raphe branches extend beyond the pseudosepta at each pole (109). The proximal raphe end at the foot pole is crook-shaped and a small aperture in the valvocopula is evident (109). In girdle view, the valvocopula are ornamented with a single row of simple poroids (110). Scale bars are 2 μm (105, 110), 1 μm (106–109).