Author: (Collett, 1904)
Hydrolagus mirabilis (Collett, 1904)
Diagnosis: body greatly tapering from a massive head and trunk to a lancet-shaped caudal fin with a very long whip-like filament. Snout short, somewhat conical, overhanging mouth. First dorsal fin short based, triangular and high, with a strong spine in front joined nearly its whole length to the fin; second dorsal fin long, continuous to origin of upper caudal fin, not more than one-third height of first and with a marked concavity in the middle part; pectoral fins clearly reaching beyond origin of pelvic fins when laid back; anal fin continuous with caudal fin, the latter with upper and lower lobes much narrower than hind part of second dorsal fin. Skin entirely smooth except for denticles on male organs. Colour: uniformly dark brown, fins darker, caudal filament whitish. Size: to 80 cm TL (but undamaged filament may comprise a third of this).
Habitat: benthopelagic on continental slopes from about 450 m to 1,200 m and probably deeper; moderately common. Food: small fishes and invertebrates. Reproduction: oviparous; egg-capsules spindle-shaped, about 13 cm long (including the short pointed tip at one end and the long horny filament at the other).
Distribution: Atlantic coasts, from northern Spain northward to Iceland, but probably more widely distributed in deep water.
Eggs, embryonic and young stages. Holt & Byrne, 1910: 13, pl. IV (fig. 1-2) (eggpurse).