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Correct name: Paralia sulcata (Ehrenberg) Cleve (vide Crawford, 1979, p. 209).

References: Crawford, 1979; Crawford, 1988, p. 422; Crawford et al., 1990.

Paralia sulcata (Ehrenberg) Cleve (Plate 14) Basionym: Gaillonella sulcata Ehrenberg. Synonym: Melosira sulcata (Ehrenberg) Kützing.

References: Ehrenberg, 1838, p. 170, Plate 21, Fig. 5; Ehrenberg, 1841a, p. 152, Plate 3, Fig. 5; Kützing, 1844, p. 55, Plate 2, Fig. 7; Cleve, 1873b, p. 7; Hustedt, 1930, p. 276, Fig. 119; Cupp, 1943, p. 39, Fig. 2; Hendey, 1964, p. 73, Plate 23, Fig. 5; Crawford, 1979. Girdle view: Cell wall extremely heavily silicified. Cells more wide than long. Valve face flattened. Chloroplasts several per cell; small discoid. Valve view: Separation valves at ends of chains without marginal spines and reduced ridges (heterovalvy). Morphometric data: Pervalvar axis 3-45 /xm; diameter 8-130 /jlm. Distribution: Paralia sulcata is a bottom form but fairly common in coastal plankton, probably cosmopolitan.

How to identify: Paralia sulcata may be identified as whole cells in water mounts and as cleaned material on permanent mounts either as sibling or single valves in girdle as well as valve views. The difference in structure of the separation and intercalary valves has to be taken into consideration. If not, this heterovalvy may cause confusion.

Genus Stephanopyxis (Ehrenberg) Ehrenberg 1845 (Plate 14, Table 17) Type: Pyxidicula aculeata Ehrenberg.

References: Ehrenberg, 1844c, p. 264; Greville, in Gregory, 1857, pp. 538 and 540, Plate 14, Fig. 109; Pritchard, 1861, p. 826, Plate 4, Fig. 74; Greville, 1865a, p. 2, Plate 1, Fig. 9; Grunow, 1884, p. 90; Gran & Yendo, 1914, p. 27, Fig. 16; Hustedt, 1930, p. 302, Figs. 140 and 147; Cupp, 1943, p. 40, Figs. 3-5; Hasle, 1973b, Figs. 91-112; Round, 1973, Figs. 1-14; Glezer et al., 1988, pp. 43 and 46, text Fig. 2: 3-7, Plate 25, Figs. 8

TABLE 17 Morphometric Data of Stephanopyxis spp.

Valve areolae in Mantle areolae in

and 9, Plate 27, Figs. 1-11, Plate 28, Figs. 1-10; Takano, 1990, pp. 240-241.

Stephanopyxis has usually been distinguished from Pyxidicula by its long siliceous external extensions of labiate processes, uniting cells in chains. Strelni-kova 8c Nikolaev (1986) did not accept this distinction and made the point that this type of linking is also found in Pyxidicula. The two genera are similar in valve structure and, despite the information in the older literature, they have girdles consisting of many bands (for Pyxidicula mediterranea, Hasle, unpublished observation made on a von Stosch culture). For the sake of convenience the name Stephanopyxis is retained for the planktonic diatoms dealt with in this chapter.

Electron microscopy revealed external valve wall structures which have been interpreted in various ways and which have a certain similarity to pseudo-loculi (Hasle, 1973b, p. 131; Round et al., 1990, p. 158). Here they are called loculate areolae with wide foramina for the sake of simplicity.

Generic characters:

Valve mantle high, more or less curved.

Valve wall with large hexagonal areolae with large external foramina. Resting spores present (semiendogenous).

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