(Figs. 4 A–F, tables 1−3)
Stephanocyathus crassus Jourdan, 1895: 21, pl. 2, figs. 17−19.—Zibrowius 1980: 100, pl. 50, figs. A–L, pl. 107, fig. K.— Ramil Blanco & Fernández Pulpeiro 1990: 27.—Cairns & Chapman 2001: 37 (tab. 1).—Brito & Ocaña 2004: 394, pl. 86, figs. A–B.—Reveillaud et al. 2008: 322 (tab. 1), 325 (fig. 4).—Altuna 2010: 21.
Material examined. Galicia Bank: Stn. G 4, 750 m, one specimen; Stn. V 4, 732 m, two specimens; Stn. V 6, 766 m, one specimen; Stn. R 2, 614 m, one specimen.
Description. Corallum solitary, unattached, stout, discoidal to patellate. Largest specimen examined has GCD= 3.77 cm and H= 1.4 cm (stn. V 6, including septa); smallest has GCD= 2.52 cm and H= 0.71 cm (stn. V 4). Base light brown, more or less flat, sometimes irregular as a consequence of regeneration, with a minute central pointed pedicel. Costae arranged according to the formula C 1 ≥C 2>C 3>C 4, well developed only distally, more or less ridged, with small pointed granules. Calices circular to slightly irregular in calicular view. Septa arranged hexamerally in four complete cycles and six systems (S 1 ≥S 2>S 3>S4, 48 septa, stn. R 2), with some supplementary septa of an incomplete S 5 sometimes present. Septa highly exsert, particularly S 1 and S 2 that are equally exsert; S 3 –S 5 progressively less exsert; S 1 −S 3 reach the columella. Septal faces with a subtle ornamentation formed by small pointed granules; inner edges close to columella, lobulated. Fossa moderately deep, containing a circular to slightly elliptical in outline columella formed by more or less straight rods, well individualized or partially fused. Corallum white.
Remarks. Specimen from stn. V 6 is slightly bigger (GCD= 3.77 cm) than the biggest specimen previously known (GCD= 3.5 cm, Zibrowius 1980). Development of a fifth cycle is not always related to a certain increase in GCD. Corallites of GCD= 2.52 cm (stn. V 6) already have a few S 5, which can be missing in bigger specimens from other stations (GCD= 3.3 cm, stn. R 2). The base of some specimens is costate, but most have their costae only apparent near calicular margin. In one specimen (stn. R 2), despite the absence of a S 5, there are rudimentary C 5 near the calicular margin. The corallum is frequently regenerated, resulting in irregularities or callosities (fig. 4 B, stn. R 2).
Stephanocyathus crassus is a rarely recorded species. For Zibrowius (1980) it is the rarest species of the genus in the north-eastern Atlantic, and only a few specimens have been collected alive. It is principally known from Azores (most part of specimens known), a station off northwestern Spain (44 º 10.5 ’N – 08º 38.4 ’W, Zibrowius 1980), and Madeira. The discovery of live specimens in four stations of the Galicia Bank is noteworthy. Stephanocyathus crassus is a new record for the region “West coast of Spain and Portugal (J)” (see Zibrowius 1980). This species was also obtained from the Galicia Bank during the 1987 SEAMOUNT 1 expedition (Zibrowius, com. pers., unpublished).