non Phormosomum luculentum (Agassiz, 1879) — $ Koehler 1895a: 224, 1895b: 228. [misidentified]; non Phormosoma uranus Thomson, 1877 — $ Koehler 1898: 7, 10–15, pl. 1, fig. 1, pl. 3, figs. 5, 6, pl. 9, figs. 49, 50 [misidentified see comments under P. uranus]; Hygrosoma petersii (Agassiz, 1880) — $ Mortensen 1903: 176, fig. 11, pl. 11, figs. 4, 27, pl. 12, fig. 42, pl. 13, figs. 8, 13; $ Koehler 1909: 217–218; Mortensen 1927a: 284–285, figs. 156.2, 158. 1, 161; $ Mortensen 1927b: 27; Grieg 1932: 41; Mortensen 1935: 202–208, figs. 118–119, pl. 13, pl. 14, figs. 1–3, pl. 15, figs. 1–2, pls. 16 –17, pl. 18, fig. 2, pl. 19, fig. 2, pl. 78, figs. 1, 3–5, 24, 25; Gage et al. 1985: 180–181; Serafy & Fell 1985: 20, fig. 17; García-Diez et al. 2005: 50; Mironov 2006: 103.
Type locality: Caribbean.
See: Grieg (1932); Mortensen (1935).
Occurrence: Atlantic, from the east coast of the USA to the Caribbean (Pawson 1982), eastwards from the British Isles to South Africa (Mortensen 1935), including the Azores (Koehler 1909), Canaries (Grieg 1932) and the Atlantis Seamount (Meteor; Mironov 2006); possibly in Bermuda’s deep waters as well (Mironov 2006).
Depth: 200– 3,800 m (Mironov 2014); AZO: 1,165 –2,870 (?3,237) m (Koehler 1909, herein).
Habitat: opportunistic scavenger, on soft ooze (Gage et al. 1985).
Larval stage: lecithotrophic (Emlet 1995).
Remarks: in a preliminary report, Koehler (1895a, 1895b, 1896c, 1898) identified specimens from the Azores and Bay of Biscay (Hirondelle, Princesse Alice and Caudan cruises) as Hygrosoma luculentum (= ‘ Phormosomum luculentum ’) and Tromikosoma uranus (= Phormosoma uranus). Mortensen (1903) questioned Koehler’s previous identifications based on the examination of a specimen belonging to H. petersii collected in the Azores by Talisman (sta 126: 38°37’00”N, 28°20’46”W, 1,258 m). Subsequently, Koehler (1909) agreed with Mortensen and re-identified the material as H. petersii. During the expedition EMEPC-LUSO (2009, 2008), animals likely to belong to this species were captured on video on the seabed of the Azorean deep waters, between S„o Jorge and Pico islands (38°34'12"N, 28°03'17"W, 1,250 m, Fig. 28D, E) and near the Hirondelle Seamount (between S„o Miguel and Terceira, 37°56'12"N, 26°10'31"W, 3,237 m, Fig. 28F).