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b R. polydactyla 26-28 valve areolae in 10/i.m, measured with TEM, information on the other species missing.

b R. polydactyla 26-28 valve areolae in 10/i.m, measured with TEM, information on the other species missing.

Rhizosolenia antennata f. semispina Sundstrom (Table 33) Commonly identified as Rhizosolenia hebetata f. semispina. Reference: Sundstrom, 1986, p. 44, Figs. 20, 114, and 116-118. Pointed otaria extending at least 3 ¡xm along the basal part of the process.

Rhizosolenia hebetata Bailey f. hebetata (Plate 27, Table 33) Synonym: Rhizosolenia hebetata f. hiemalis Gran. References: Bailey, 1856, p. 5, Plate 1, Figs. 18 and 19; Gran, 1904, pp. 524-527, Plate 27, Figs. 9 and 10; Hustedt, 1930, p. 590, Fig. 337; Cupp, 1943, p. 88, Fig. 50a; Drebes, 1974, p. 56, Fig. 41; Sundstrom, 1986, p. 47, Figs. 18, 112, and 113. Process heavily silicified, no otaria.

Rhizosolenia hebetata f. semispina (Hensen) Gran (Plate 27, Table 33) Basionym: Rhizosolenia semispina Hensen.

PLATE 27 Rhizosolenia borealis: ventral view. Scale bar = 50 /¿ra. Rhizosolenia polydactyla: upper theca f. polydactyla and the lower theca f. squamosa. Scale bar = 50 ¿im. Rhizosolenia antennata f. antennata: Scale bar = 20 fim. Rhizosolenia hebetata: f. hebetata: (a) ventral and (b) lateral view. Scale bar = 20 pm. Rhizosolenia hebetata f. semispina: ventral view. Scale bar = 20 |um. Rhizosolenia sima f. sima: ventral view. Scale bar = 50 /um. Rhizosolenia sima f. silicea: ventral view. Scale bar = 50 /xm. All figures after Sundström (1986).

References: Hensen, 1887, p. 84, Plate 5, Fig. 39; Gran, 1904, Plate 27, Figs. 11 and 12; SundstrOm, 1986, p. 48, Figs. 19, 20, 114, and 116-118.

Pointed otaria extending at least 3 /¿m along the basal part of the process. Remarks: Although R. antennata f. semispina and R. hebetata f. semispina are almost indistinguishable with both LM and EM, Sundstrom (1986) regarded the species as separate taxa because of the widely different distribution and the great morphological dissimilarity between their nominate forms.

Rhizosolettia polydactyla Castracane f. polydactyla (Plate 27, Table 33) Synonym: Rhizosolettia styliformis var. oceartica Wimpenny pro parte. References: Castracane, 1886, p. 71, Plate 24, Fig. 2; Wimpenny, 1946, p. 279, Text Fig. le; Sundstrom, 1986, p. 24, Figs. 7-9, 70-73, 74, 76, 77, and 79.

Otaria extending to about half the length of the thicker basal part of the process.

Rhizosolettia polydactyla f. squamosa Sundstrom Reference: Sundstr&m, 1986, p. 26, Figs. 8, 9, 73, 75, and 78. Bands in two or a multiple of two columns. Process coarsely structured; otaria lacking. "Exogenous resting spore" of f. polydactyla?

Rhizosolettia sima Castracane f. sima (Plate 27, Table 33) References: Castracane, 1886, p. 71, Plate 24, Fig. 11; Van Heurck, 1909, Plate 4, Fig. 70; Sundstrom, 1986, p. 62, Figs. 28 and 144-149. Process basal part bulbous; distal tube thin walled. Otaria large, extending along the basal part of the process.

Rhizosolettia sima f. silicea Sundstrom (Plate 27, Table 33) References: Van Heurck, 1909, Plate 4, Fig. 71; Sundstrom, 1986, p. 63, Figs. 29 and 150-154. Process heaviliy silicified, usually with uneven longitudinal ridges; no otaria. "Resting spore" of f. sima?

Distribution:

R. antennata, R. polydactyla, and R. sima—southern cold water region. R. hebetata—northern cold water region.

3. More than two columns of segments.

Rhizosolenia crassa Schimper in Karsten (Plate 28, Table 34) References: Karsten, 1905, p. 99, Plate 11, Fig. 6; Sundstrom, 1986, p. 59, Figs. 26, 27, and 139-143. Two and four columns of bands within a single cell. Otaria prominent, bordering valve apex and basal part of process; distal margin concave.

Rhizosolenia clevei Ostenfeld var. clevei (Plate 28, Table 34) References: Ostenfeld, 1902, p. 229, Fig. 6; Sournia, 1968, p. 78, Plate 10, Fig. 68; Sundstrom, 1984, p. 348, Figs. 1 and 4-9; Sundstrom, 1986, p. 53, Figs. 21, 121, 122, and 125.

Otaria arising at valve apex, extending along the basal part of the process. Host for the blue-green Richelia intracellularis.

Rhizosolenia clevei var. communis Sundstrom (Plate 28, Table 34) References: Sundstrom, 1984, p. 348, Figs. 2, 3, and 10-15; Sundstrom, 1986, p. 54, Figs. 22, 23, 123, 124, 126, and 127. Bands in two columns, otherwise as the nominate variety.

Rhizosolenia hyalina Ostenfeld in Ostenfeld & Schmidt.

(Plate 28, Table 34)

Synonym: Rhizosolenia pellucida Cleve.

References: Cleve, 1901a, p. 56, Plate 8, Fig. 4; Ostenfeld & Schmidt, 1901, p. 160, Fig. 11; Sournia, 1968, p. 79, Plate 3, Fig. 19; Sundstrom, 1986, p. 76, Figs. 34 and 190-194. Process slightly bent near the end of the otaria. Otaria narrow, extending along process for ca. 4-6 ¿im.

Rhizosolenia castracanei H. Peragallo var. castracanei (Plate 28, Table 34) References: Peragallo, 1888, p. 83, Plate 6, Fig. 42; Cupp, 1943, p. 94, Fig. 54; Sundstrom, 1986, p. 37, Figs. 15, 16, 102-104, and 108-111. Bands coarsely structured. Valve apex shallow. Otaria confined to valve proper.

Rhizosolenia castracanei var. neglecta Sundstrom (Plate 28, Table 34) Reference: Sundstrom, 1986, p. 39, Figs. 17 and 105-107.

Bands in two columns. Valves of narrow cells similar to those of R. styliformis.

Rhizosolenia debyana H. Peragallo (Plate 28, Table 34) References: Peragallo, 1892, p. Ill, Plate 2, Figs. 7 and 7a; SundstrOm, 1986, p. 57, Figs. 24, 25, and 128-138. Valve and otaria similar in shape to those of R. castracanei var. castracanei; band areolae smaller. Remarks: The number of columns of segments and the size of cell diameter are related to a certain extent. In Rhizosolenia crassa two columns of segments were observed in cells of all sizes and four columns in cells of 115-140 /i,m in diameter but not in the narrower ones.

Rhizosolenia temperei H. Peragallo (Plate 29, Table 34) References: Peragallo, 1888, p. 83, Plate 5, Fig. 40; Hustedt, 1930, p. 605, Fig. 349; Sundstrbm, 1986, p. 66, Figs. 30 and 155-163. Valve contour sigmoid. Distal part of valve abruptly narrowed. No otaria.

R. castracanei var. neglecta

R. debyana

TABLE 34 Morphometric Data of Rhizosolenia spp. with More Than Two Columns of Segments

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