(Fig. 7)
Serpula minax Grube, 1878: 269 –271, pl. 15, fig. 5 [Philippines; original description].
Eupomatus minax. — Willey 1905: 314 [Sri Lanka].
Serpula (Hydroides) monoceros.— Gravier 1906 a: 110 –111 [Red Sea; description]; 1906 b pl. 8 fig. 288 [same]; 1908: 115–117, figs 467–472 [same].
Hydroides monoceros. — Pixell 1913: 76 –77 [Zanzibar, Red Sea; diagnosis]; Fauvel 1919: 342 [Gambier Islands]; 1923: 48 [same]; 1930: 63 [Sri Lanka]; 1947: 95–96, fig. 89 e [Gambier Islands]; 1953: 460 [Sri Lanka]; Day 1957: 118 [Inhaca Island, Mozambique]; 1967: 808, fig. 38.4o–p [same]; Hartman 1959: 453 [synonymy]; Straughan 1967 a: 31 [Heron Island, Qld]; 1967 b: 221 [Havannah Island, Qld]; Gibbs 1969: 446 [Solomon Islands]; Kumaraswamy Achari 1969: 40 [Sri Lanka]; Pillai 1971: 71 [Sri Lanka]; Amoureux et al. 1978: 145, fig. 12 [Gulf of Eilat]; Lewis 1979: 7 [Qld; fouling]; Vine & Bailey-Brock 1984: 141 [Sudanese Red Sea]; Chandra Mohan & Aruna 1994: 60 [India; shipfouling].
Hydroides minax. — Fauvel 1939: 361 –362 [Vietnam]; 1953: 460 [Sri Lanka]; Pillai 1960: 8 –10, fig. 3 a–e [Sri Lanka]; 1971: 110 [Sri Lanka]; Wu 1968: 45 [Taiwan]; Kumaraswamy Achari 1969: 40 [Sri Lanka]; Imajima 1976 a: 234 –235 [diagnosis; Japan]; 1976 b: 129–130, fig. 5 [Tanega-Shima, South Japan; description]; 1982: 42 [Micronesia]; 1987: 77 [Okinawa, Japan]; Zibrowius 1979: 133 –134 [ship’s hull in Toulon, France]; Zibrowius & Bitar 1981: 160 [ship-transported to Mediterranean]; Imajima & ten Hove 1984: 48 [Majuro; Lizard Island, Qld; synonymy]; 1986: 3 [Solomon Islands]; Vine & Bailey-Brock 1984: 141 [Sudanese Red Sea]; Vine 1986: 90 [Sudanese Red Sea; figure]; Bailey-Brock 1987: 282 [Tonga]; Ben-Eliahu & ten Hove 1992: 40 –43, 45, 47, 52–53 [Red Sea, Lessepsian migrant to the Levantine Mediterranean]; ten Hove 1994: 108 [Seychelles]; Fosså & Nilsen 1996: 139 [Indo-Pacific; symbiotic in corals]; 2000: 141 [same]; Hassan 1998: 50, figure [Red Sea; diagnosis]; Fiege & Sun 1999: 119, fig. 9 A–C [South China Sea]; Sun & Yang 2000: 126, fig. 5 G–J [South China Sea]; ten Hove & Ben-Eliahu 2005: fig. 1 h [Red Sea, Indonesia]; Kupriyanova et al. 2008: 428, 430–431 [Lizard Island; DNA data]; ten Hove & Kupriyanova 2009: 53 [name only]; Pillai 2009: 120, figs 15 A–G, 16 A–F [Kimberley, WA]; Bailey-Brock et al. 2012: 969, 972 [Enewetak, Majuro, Marshall Islands]; Sun et al. 2015: 53 –56, fig. 16 [WA, NT, Qld, Australia].
Not Hydroides minax.— Gibbs 1971: 203 [Solomon Islands; see H. albiceps].
Material examined. AM W. 16982, near Bird Islet, 14 ° 40 'S, 145 ° 28 'E, experimental fouling grid C, 7 m, coll. P. Hutchings & P. Weate, 1979, det. H. ten Hove; AM W. 42357, Yonge Reef, back reef, 14 ° 36 'S, 145 ° 37 'E, in cave, coll. R. Smith, Nov 1985, det. E. Kupriyanova; AM W. 42358, Yonge Reef, back reef bommie, 14 ° 36 'S, 145 ° 37 'E, on ledge, 5 m, coll. R. Smith, 7 Nov 1985, det. E. Kupriyanova; AM W. 42359, Yonge Reef, 14 ° 36 'S, 145 ° 37 'E, coll. R. Smith, det. E. Kupriyanova; AM W. 46530, inter-reef sand, 14 ° 23 ' 24 "S, 145 ° 16 ' 24 "E, artificial substrate, 10 m, coll. M. Timmers, 10 Feb 2009; SAM E 3597, stn.G 229, near Bird Islet, 7–8 m, coll. G. Rouse & E. Kupriyanova, 24 Oct 2005; ZMA V.Pol. 3447, near Bird Islet, grid C, experimental fouling panels, coll. P. Hutchings & P. Weate, det. H. ten Hove 1981, retained from AM W. 16984 – 6; ZMA V.Pol. 5035, stn. 21, south of South Island, 14 ° 42 'S, 145 ° 28 'E, sloping silty reef, little coral cover, 18–20 m, coll. H. ten Hove & P. Hutchings, 6 Mar 1986.
Diagnosis. Opercular verticil with 7–11 spines, dorsal one stout, elongated, terminating in three sharply pointed ventrally curving hooks that may be of similar size, but generally one large terminally and two smaller ones laterally; other verticil spines short, curved outwards, with pointed tips. Spinules and central tooth absent. Funnel with 22–26 chitinized radii ending in swollen or sharp tips, base of funnel elongated, chitinized, merging into constriction. Grooves separating radii extending 1 / 2 of funnel length (Fig. 7).
Remarks. Hydroides minax can be easily confused with H. lirs n. sp. (see Remarks after description of H. lirs n. sp.). In addition to morphological differences, the two species appear to differ ecologically: specimens of H. minax were collected from coral rubble or rocks, while those of H. lirs n. sp. were found embedded in living corals.
Distribution. Widely distributed in the Indo-West Pacific, Lessepsian migrant to the Levant Mediterranean.