The synthesis of many years' research carried out by members of the British Phycological Society in collaboration with The Natural History Museum, this is the eighth in a series of books being published under this title covering all the British and the majority of the northern Atlantic seaweeds. Seaweeds of the British Isles, Volume 1 Part 3b is stylistically similar to earlier titles in the series and is written by leading authorities in red algae. The sub-class and all orders, families, genera and species are described, notes on ecology and distribution given, and each named species is illustrated by one or more half-tones showing distinctive features. User-friendly keys are provided to enable identification of genera and species. Special features of Seaweeds of the British Isles, Volume 1 Part 3b are the comprehensive introduction and complete re-evaluation of the British Isles taxa of the sub-class, including a revision of the species of Porphyra.