Order 3. Chætangiaceæ. Galaxaura has a thallus thickly incrusted with lime.
Order 4. Gelidiaceæ. Naccaria, Gelidium.
Sub-Family 2. Gigartinales. The fertilised auxiliary cell grows towards the thallus, to produce the gonimoblasts. Procarpia generally present.
Order 5. Acrotylaceæ. Acrotylus.
Order 6. Gigartinaceæ. Gigartina, Phyllophora, Ahnfeltia; Chondrus crispus, with dark red, dichotomously branched thallus, is common on the coasts of Scandinavia and Great Britain.
Order 7. Rhodophyllidaceæ. Rhodophyllis, Euthora; Cystoclonium purpurascens is common, and sometimes the ends of its branches may be modified into tendril-like haptera.
Sub-Family 3. Rhodymeniales. The fertilised auxiliary cell forms the gonimoblast on the side away from the thallus. Procarpia are abundantly produced.
Order 8. Sphærococcaceæ. Gracilaria.
Order 9. Rhodymeniaceæ. Rhodymenia palmata is a common species. Lomentaria, Chylocladia, Plocamium.
Order 10. Delesseriaceæ. Delesseria sanguinea; D. alata and D. sinuosa are handsome forms which are not uncommon.