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Table of Contents

(a) Meloseirinæ.—Frustules short, in chains.

(b) Coscinodiscinæ.—Frustules disc form, usually single, rarely in short chains.

(a) MELOSEIRINÆ

1. Meloseira.—Valve punctate, with a constriction or furrow between edge of valve and girdle.

2. Gaillonella.—Valve punctate, with a circular collar or crest near edge of valve.

3. Lysigonium.—Valve punctate, neither keeled nor constricted.

4. Hyalodiscus.—Valve punctate in the centre; border with decussating radial lines.

5. Stephanopyxis.—Border of valve with a crown of thorns; valve areolate.

6. Pyxidicula.—Valve areolate, with a border of spines.