Key To Species

la. Valve center with large (up to 50 /xm in diameter) nonareolated area bordered by an irregular ring of processes

E. gazellae8 (Janisch ex Grunow) Hustedt lb. Valve center irregularly areolated with nonareolated areas interspersed, central processes larger and scattered

- E. rex8 (Rattray) Hendey in Wiseman & Hendey

Distribution: Warm water region to temperate.

How to identify: Although the unusually large size may distinguish the genus in water mounts, examination of cleaned material on permanent mounts is needed to distinguish between the two species.

Remarks: Marginal labiate processes are present in E. gazellae (Round,

1980), but were not seen in E. rex (Rivera et al., 1989).

Genus Palmeria8" Greville 1865 (Plate 18, Table 22) Type: Palmeria hardmaniatia Greville.

' Basionyms: Coscinodiscus gazellae Janisch ex Grunow and Coscinodiscus rex Rattray, respectively.

80 Palmeria Greville 1865 is a later homonym of Palmeria F. von Miiller 1864 and was given the new name Palmerina Hasle 1995 (Diatom Research 10, 357-358).

Synonym: Hemidiscus hardmanianus (Greville) Mann. References: Greville, 1865b, p. 2, Plate 5, Figs. 1-4; Ostenfeld, 1902, p. 222, Figs. 1 and 2; Mann, 1907, p. 316; Allen & Cupp, 1935, p. 152, Figs. 91 and 91a-91e; Simonsen, 1972, p. 270, Fig. 12; von Stosch, 1987, pp. 31-41, Figs. 1-45.

Generic characters:

Valves semicircular.

Hyaline central area.

Radial areolation with incomplete striae inserted from the margin. Distinct hyaline lines associated with marginal processes. Two processes larger than the others.

KEY TO SPECIES (von Stosch, 1987, p. 32)

la. Valve face approximately plane P. hardmaniana Greville lb. Valve face excavated by deep narrow fold parallel to dorsal circumference of valve face and usually settled by epiphytic ciliates

P. ostenfeldii9 (Ostenfeld) von Stosch

Distribution:

P. hardmaniana—warm water region.

P. ostenfeldii—Gulf of Thailand and Townsville, Australia (von Stosch, 1987), but may have a much wider distribution because it was confused with the former species in the past. How to identify: The valve morphological structures are seen with LM by examination of material mounted in air or Pleurax (von Stosch, 1987). In P. hardmaniana, the ventral line of small labiate processes (those along the straight valve margin) is ca. 10 areolae away from the margin. In P. ostenfeldii, it is ca. 20 areolae from the straight margin in its middle part.

TABLE 22 Morphometric Data of Palmeria spp.

Species

Length (p.m)

Width (p.m)

Areolae in 10 p,m

P. hardmaniana

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