Familia Edwardsiidae

Andres, 1881

Athenaria with an elongated, often vermiform column which is usually differentiated into two or more regions. Aboral end rounded, its structure variable, usually bearing adhesive rugae and sometimes cinclides; limbus absent. Periderm usually present on the column. Mesenteries consist of eight macrocnemes bearing strong retractor and parietal muscles, gonads and filaments, and a variable number of microcnemes which lack muscles, gonads and filaments, usually being restricted to the most distal part of the column. Sphincter muscle always absent.

Two genera of this family possess nemathybomes, these are externally opening pockets in the mesogloea of the column wall which contain batteries of large nematocysts (b-mastigophores). Sometimes they form externally visible tubercles, sometimes they are only discernible in fixed, sectioned material. Measurements of the nematocysts from the nemathybomes are provided as these may be used to determine the identity of preserved specimens.

The condition of the ciliated tracts is an important generic character: in Edwardsia and Edwardsiella they are very short, about 1-3 mm, and occur just below the actinopharynx; in Scolanthus and Nematostella they run the whole length of the fertile region of the macrocnemes and are discontinuous, being broken into short lengths.

Edwardsiids are easily distinguished from other anemones and indeed have often been mistaken for worms. The occurrence of only eight macrocnemes is unusual and easily determined, even where thick periderm is present, being ; indicated by eight shallow longitudinal grooves in the periderm. The periderm, which is present in most species, forms a more or less dense covering adherent to l the column. It resembles tree bark in appearance but is soft, flexible and very elastic; it may slough away in specimens that are left unburied.

Members of this family are worldwide in distribution and many species have been described. However, due to their shyness, generally small size and burrowing habits, edwardsiids are seldom found, or at least recognized, and hence knowledge of their distribution is patchy.