McLaughlin 1992, Diatom Research 7: p. 96, figs 1–11.

Materials examined:— Oregon, Klamath Co., Forest Road, No. 3683-A, 6.6 miles W of Beatty, N of highway 140. CAS Accession Numbers 600120, 600121, 600122, Slide Numbers 436069, 436070, 436071, 436072, 436073, 436074 (CAS!)

We observed two morphotypes in populations we examined. They are almost exactly the same except for size and valve outline. We present descriptions for both morphotypes even though at this time we recognize them as the same taxon, C. jonesii.

Morphotype 1 (Figs 70, 72, 73, 75)

Description:—Valve outline rhomboid to ellipsoid, but large forms are nearly circular. Major axis is 20 to 95 µm, minor axis 11 to 93 µm. Central area is elongated, asymmetrically undulate with the depressed portion shallower than the rise of the elevated part. Central area occupies 1/3 to 1/2 of the total valve face and contains areolae arranged in more or less radial rows. Valve face fultoportulae are absent. Striae number 7–9/ 10 µm, consisting of 2–3 rows of small puncta (with up to 30 puncta in 10 µm measured radially), and separated by interstriae. Alveolae are complex and simple. Marginal fultoportulae have three satellite pores and are located on all recessed costae within alveolar chambers internally. They open by short tubes on the external valve surface. One or two rimoportulae are present also on recessed costae between two alveolar openings. A closed valvocopula and several open copulae without puncta are present.

Morphotype 2 (Figs 71, 74, 76, 77)

Description:—Frustules solitary, elliptical-lanceolate in valve view, with several girdle bands. A closed valvocopula has numerous plaques along the valve. Several open bands, as a valvocopula, lack areolae. Dimensions of major axis of valves vary from 11.7 to 42.7 µm, of minor axis from 7 to 30 µm. Valve face is distinctly divided into two zones: a marginal alveolate zone and a transversely undulate, elongated areolate central area. A narrow, irregular hyaline area separates these two zones. Central area is elliptical, symmetrically undulate: elevated and depressed parts are almost equal. Areolae with internal domed cribra and external foramina are arranged mainly irregularly. One valve face fultoportula with two satellite pores internally and a round thickened aperture externally can be seen within the central area, rarely can be absent. Striae, 10–12 in 10 µm, are slightly radiate in the middle part of the marginal zone and strongly radiate towards the valve ends. Striae consisting of two-four rows of small puncta (40–50 puncta in 10 µm) are divided by interstriae (costae). Alveolae are complex and simple, 10–12 in 10 µm. Marginal fultoportulae have three satellite pores internally and open by short tubes externally. They are positioned on all recessed costae within alveolar chambers on the internal valve surface. One or two rimoprtulae are sessile internally, and each is located on a costa between two alveolar openings in the pole area. Rimoportulae open by a round apertures externally. Spines can be present on the valve face/mantle junction, but they are often broken.