In the family Alepocephalidae there are ca. 19 valid genera (Markle, personal communication). Whilst luminescence has never been observed, there are four genera, Xenodermichthys, Photostylus, Rouleina and Microphotolepis, which contain species bearing structures that have been interpreted anatomically as photophores (Herring & Morin, 1978). Among these four there is a remarkable diversity of photophore structure. The photophores of Xenodermichthys and Photostylus are similar in having well developed central cores (reddish violet in Xenodermichthys) and reflector layers, yet those of Xenodermichthys are sessile whilst those of Photostylus are borne on stalks (e.g. von Lendenfeld, 1887; Best & Bone, 1976). Not all species of Rouleina have light organs but where they are present they are sessile. Photophore structure of Rouleina has been examined only in R. maderensis Maul and was found there to be rather degenerate in adults (Markle, 1978). The light organs of Microphotolepis multipunctata Sazanov and Parin differ yet again in being scale covered, which contrasts with the naked photophores in the other three genera (Sazanov & Parin, 1977). The abundance and distribution of photophores in adults also varies with genus and species. Thus in Microphotolepis and Xenodermichthys they are extremely numerous and regularly arranged but in Photostylus they are few and less ordered (Günther, 1887; Beebe, 1933; Sazanov & Parin, 1977). In different species of Rouleina photophores may be relatively abundant and regularly arranged or few in number without such regular pattern (Maul, 1948; Uyeno & Kishida, 1977; Markle, 1978).