Eudendrium rugosum Fraser, 1940a: 575, pl. 32, fig. 1.
Holotype. USNM 43433: North Atlantic Ocean, Flemish Cap, R / V Albatross Sta. 2693, 46°53’N, 44°39’30”W, 11 August 1886, large beam trawl, 143 m, two larger and a few smaller fragments of a colony, with hydrocauli up to 1.3 cm high, without hydranths but with a few male gonophores, labelled “ type ”; ethanol.
Paratype. BCPM 976-00250-001: North Atlantic Ocean, 46°53’N, 44°39’30”W, 11 August 1886, 139 m, several colony fragments, up to 5 mm high, in very poor condition, gonophores not seen, labelled "co-type"; 60% IPA.
Type locality. International waters: North Atlantic Ocean, Flemish Cap, 46°53’N, 44°39’30”W (Fraser 1940a).
Current status. Valid.
Remarks. Fraser (1940a) designated USNM 43433 as the “ type ” of Eudendrium rugosum. That name-bearing type material is recorded, correctly, as a holotype in the NMNH online database. Other specimens at the RBCM (BCPM 976-00250-001), labelled “co-type”, constitute paratype material.
The hydroid of Eudendrium rugosum is small (ca. 15 mm high) and poorly characterized. Fraser (1940a) did not describe or illustrate its hydranths, and only male gonophores were present in his material. Examination of the holotype confirm this account. The cnidome has yet to be described. It is listed as valid in Cairns et al. (2002) and WoRMS, but discovery and examination of new material, particularly from the general type locality, is needed to better define and distinguish the species.