“Coelosphaera (Coleosphaera) tubifex Thomson, 1873 (Fig. 2A).
Synonymy. Coelosphaera tubifex Thomson, 1873: 484; ? Carter, 1876: 472. Histoderma appendiculatum Carter, 1874a: 220, pl. XIV figs 23-25, pl. XV fig. 39; Carter, 1876: 472; Coelosphaera appendiculata; Dendy, 1922b: 102.
Material examined. Neotype (proposed herein): BMNH 1882.7.28.27-labeled ‘Histoderma appendiculata Carter, Porcupine stat. 24, North Atlantic, one of Carter’s syntypes’. Paratype: BMNH 1882: 7:28:38-North Atlantic, ‘Porcupine’ stn. 2 (syntype of Histoderma appendiculata).
Description. Subglobular (Fig. 2A) with several long narrow tubular fistules of different lengths, some of which are open and presumably function as oscules. Inside virtually hollow. Size not recorded. Surface smooth. Consistency tough, parchment-like. Colour light grey. Skeleton a dense tangential crust of intercrossing megascleres at the surface; choanosome without spicule tracts or fibers, just a pulpy mass of organic material, containing the canal system and loose spicules. Spicules smooth tylotes of 520 x 6µm, long smooth stylotes resembling the tylotes but with one end tylote and the other bluntly stylote, up to 900 X 14 µm; arcurate isochelae of about 25-30 µm. Distribution and ecology. North Atlantic and Arctic, deep sea, 200-1500m depth.
Remarks. This species has been ignored in the literature, whereas a very similar species, C. appendiculata (Carter, 1874a as Histoderma) is recorded several times. It is likely that both are synonyms. Dendy (1922b) suggested that the type specimens of Histoderma appendiculatum (BMNH 1882.7.28.27, 38) from H.M.S. ‘Porcupine’ Expedition stat. 24, are the same material as that described as Coelosphaera tubifex by Thomson, but the proof of that is now wanting. Carter himself (1876) hesitatingly admitted that the two could be synonymous. In the absence of Thomson’s material, the type of Carter registered as BMNH 1882.7.28.27 is here proposed as a neotype for Thomson’s species. A second North Atlantic species is C. physa (Schmidt, 1875 as Desmacidon) differing from C. tubifex in lacking sigmas and possessing trichodragmas instead. Carter (1886c: 452) realized his name [Histoderma] was preoccupied by a fossil annelid, and replaced it by Histioderma, with the same type species, and thus it becomes a junior synonym of Coelosphaera.”
(Hooper & Soest, 2002: 531-532)
