Abstract
Australia has a rich diversity of species belonging to the order Dictyotales. Sixteen genera and 41 species are recorded for temperate southern coasts (Womersley 1987) and 13 genera and 43 species for tropical to warm temperate northern coasts (Lewis 1985) giving a total of 17 genera and 73 species. Stoe chospermum is the only genus in the order not previously recorded from Australian coasts. Kiitzing (1843) erected the genus Stoechospermum and in cluded Zonaria marginata C. Agardh as Stoechospermum marginatum (c. Agardh) Kiitzing. Subsequently, four more species were added to the genus: Stoechospermum patens J. Agardh (1848) from the Red Sea, Stoechospermum maculatum (J. Agardh) J. Agardh (1848) from India, Stoechospermum polypodioides (Lamouroux) J. Agardh (1848) from the Antilles and Stoechospermum suhrii Kiitzing (1859) from South Africa. S. maculatum and S. patens were later reduced to synonyms of S. marginatum (Zanardini 1858; Papenfuss 1977) and S. suhrii was transferred to Dilophus (Papenfuss 1940). The status of S. polypodioides, known only from the type specimen, is not clarified. Stoechospermum is a distinctive genus characterized by elongate sporangial sori oriented parallel to the thallus margin, and this feature is not found elsewhere in the Dictyotales. S. marginatum has a reported geographical distribution (Fig. I) from Inthaca Peninsula, Mozambique (26°S, 33°E, AD 57995, Isaac, 30.vi.1954) north to the Red Sea and south along the Indian subcontinent to Sri Lanka (6-100N, 80-82°E, Durair atnam 1961). This paper extends the distribution to the north ern Western Australian coastline and describes the thallus morphology and vegetative anatomy along with the arrange ment and structure of sporangial sori of Australian specimens.
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