Medusae are common constituents of the meso-and bathypelagic fauna. Small, transparent trachyline hydromedusae are usually most abundant, but the larger (2–10 cm diameter) pigmented coronate scyphomedusae are often collected in trawl nets (Thurston, 1977; Roe, James & Thurston, 1984; Larson, 1986) or observed from submersibles (Mackie & Mills, 1983; Mackie, 1985; Larson, Madin & Harbison, unpublished observations). Larger (30–70 cm) deep-sea semaeostome scyphomedusae are only infrequently collected in nets (Harbison, Smith & Backus, 1973; Larson, 1986), and would appear to be the rarest forms. For example, Thurston (1977) collected over 16000 midwater medusae in trawls yet he did not report taking a single mesopelagic semaeostome. However, recent investigations using submersibles have shown that these medusae are much more common than net hauls alone would suggest (Smith, 1982).