Diploneis galloprovincialis

Valves of both taxa linear-elliptical with broadly rounded ends. Length 16–27 (vs. 18–40 in D. marginestriata) μm, breadth 7–9 (vs. 8–11) μm; ratio length- to-breadth 2.3–2.9 (vs. 2.2–3.6) Zone of the canals 3–4 (vs. 3–6) μm broad. Striae 18–20, on average 19, (vs. 17–18) in 10 μm. Thus the maximum length of examined specimens of D. galloprovincialis is distinctly smaller, breadth of valves and canal systems is moderately smaller, and stria density is higher than in D. marginestriata.

Fine-structural characteristics that separate the two taxa are discernible in external SEM view as follows (see Figs 171: 1–4 vs. Figs 164: 13–15; 165: 1–4). First, the adaxial areolae are prolonged transapically in subproximal and sub- distal parts of the canals only in D. galloprovincialis; they are isodiametrically compact in D. marginestriata. Secondly, in D. marginestriata sinuous openings and volate structures are simple rather than complicatedly branching as in D. galloprovincialis (Figs 164: 14, 15 vs. Figs 171: 1–3). Thirdly, unlike D. gallo- provincialis, D. marginestriata exhibits little warts (pustules) that are irregularly distributed over the external wall (Fig. 164: 14). Larger unstructured openings on either side across the external wall into the canals are absent from both taxa.

• Author
  Lange-Bert., Fuhrmann and V. Peeters 2020
• Length Range
  16–27 µm
• Width
  7–9 µm
• Striae in 10µm
  18–20