Sertularia subtilis Fraser, 1937b

Sertularia rugosissima Thornely, 1904: 118, pl. 2, fig. 4.

Sertularia hupferi Broch, 1914: 34, figs. 9a–c.

Tridentata rugosissima Stechow, 1923: 205 .

Sertularia subtilis Fraser, 1937b: 3, pl. 1, fig. 4.

Geminella subtilis .— Vannucci Mendes, 1946: 572, pl. 4, figs. 42, 43.

Holotype. USNM 43288: Puerto Rico, off NE coast, Johnson-Smithsonian Deep-Sea Expedition Sta. 68, 18°23’35”N, 65°37’10”W, 24 February 1933, 18 m, R/ V Caroline, one colony, 3 mm high, in fairly good condition, without gonothecae, coll . Paul Bartsch, labelled “ type ” and “ holotype ”; ethanol.

Schizoholotype. BCPM 976-00681-001: Puerto Rico, two colony fragments (distal part of hydrocaulus with four pairs of hydrothecae, 1.9 mm high; basal part of hydrocaulus and stolon, 2.8 mm high), in good condition, without gonothecae; slide.

Type locality. Puerto Rico: northeast coast, 18°23’35”N, 65°37’10”W, 10 fm (18 m) (Bartsch 1933; Fraser 1937b).

Current status. Invalid.

Remarks. Sertularia subtilis was described from a single, sterile, 3-mm-high colony collected during the Johnson-Smithsonian Deep-Sea Expedition to Puerto Rico and vicinity (Fraser 1937b). The small specimen at the NMNH (USNM 43288), designated by Fraser as the holotype, is currently listed as a syntype in the online database of that museum. Material on a slide in the Fraser Hydroid Collection at the RBCM (BCPM 976-00681-001), from Puerto Rico, is regarded here as a fragment of the holotype (schizoholotype), because no other records of this species were known to Fraser (1944a, 1947a). No expedition station number is currently recorded under S. subtilis in either the NMNH or the RBCM databases, or in the records of Fraser (1937b) and Arai (1977), but the coordinates and depth of collection given by Fraser correspond with Station 68 in Bartsch (1933). A label confirming that station number exists in the vial containing the holotype. A colony of Tridentata turbinata (Lamouroux, 1816), a much larger species of hydroid, occurs in close proximity to the holotype of S. subtilis .

This species has been assigned in WoRMS, and in several papers on hydroids of the warm western Atlantic (e.g., Migotto 1996; Galea 2008), to the synonymy of Sertularia rugosissima Thornely, 1904 . Inclusion of that species in Sertularia Linnaeus, 1758 is patently incorrect in differing greatly from Sertularia argentea, type species of the genus. It is referred here to Tridentata Stechow, 1920, as T. rugosissima, based on the known morphology of its trophosome and gonotheca. Also considered a synonym of T. rugosissima is Sertularia hupferi Broch, 1914 .