Key To Species

la. Undulation of valve pronounced 2

lb. Undulation of valve evident but not pronounced 3

2a. A marginal strutted process on every second, occasionally on every interstria; valve without marginal chambers. . C. litoralis Lange & Syvertsen 2b. Marginal strutted processes grouped in pairs or triplets; valve with prominent marginal chambers covering three or four alveolus openings

C. stylorum Brightwell

3a. A marginal strutted process on every second to fourth interstria; valve with marginal chambers covering two alveolus openings

C. striata1 (KUtzing) Grunow in Cleve & Grunow

3b. A marginal strutted process on every third or fourth interstria; valve without marginal chambers C. caspia Grunow

Distribution:

C. caspia—northern temperate region, euryhaline.

C. litoralis—southern and northern temperate region, coastal, marine

(Lange & Syvertsen, 1989; Sancetta, 1990).

C. striata—northern temperate region, littoral.

C. stylorum—warm water region to southern temperate region, littoral. How to identify: The species may be identified with light microscopy (LM) as cleaned valves mounted in a medium of a high refractive index. Remarks: Nagumo & Ando (1985) made a comparative study of C. stylorum and a species identified as Cyclotella sp. The latter is most likely C. litoralis.

Genus Detonula Schutt ex De Toni 1894 (Plate 1, Table 2)

Lectotype: Detonula pumila (Castracane) Gran (vide Round et al., 1990, p.

Basionym: Lauderia pumila Castracane.

Synonyms: Schroederella delicatula Pavillard, Thalassiosira condensata Cleve (for other synonyms see Hasle, 1973a, p. 18).

1 Basinoym: Coscinodiscus striatus KUtzing.

Species

Pervalvar axis (|j,m)

Diameter (lim)

Marginal processes in 10 pun

Areolae in 10 |jun

D. confervacea D. pumila D. moseleyarta

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