(Figs. 2 N– O, tables 1–3)
Caryophyllia seguenzae Duncan, 1873: 314, pl. 44, figs. 4−6.—Zibrowius 1980: 67, pl. 27, figs. A–J.—Altuna & García Carrascosa 1990: 56.—Altuna Prados 1994 a: 455, pl. 11, figs. B, D–E, pl. 12, fig. A.—Altuna Prados 1994 b: 55.—Altuna Prados 1994 c: 78 (fig. 1).—Altuna 1995: 88, fig. 3.—Cairns & Chapman 2001: 35 (tab. 1).—Reveillaud et al. 2008: 322 (tab. 1), 325 (fig. 4).—Altuna 2010: 21.
Material examined. Le Danois Bank, 2008: Stn. D 4 V, 1084 m, three dead and broken specimens, rather worn, perhaps subfossil. Le Danois Bank, 2009: Stn. V 3, 999 m, an adult specimen alive, and five young dead, worn; Stn. V10, 1222 m, two dead and worn specimens, one of them a juvenile.
Description. Largest corallum examined solitary and unattached, trochoid and somewhat compressed laterally (H= 3.45 cm, stn. V 3). Base ended in a pointed pedicel slightly curved. Wall strongly costate and finely granulated; C 1−2>C 3>C 4–5; C 1 –C 2 very prominent, well-delineated; C 1 −C 3 ridged, C 4 −C 5 flat. Calice wide and faintly elliptical (GCD= 4.16 cm; LCD= 3.38 cm; GCD: LCD= 1.23). Septa arranged hexamerally in five cycles according to the formula S 1−2>S 3>S 4 ≥S 5 (S 5 incomplete - 91 septa). Upper septal margins smooth and septal faces with scarce minute granules; S 1 and S 2 subequal and highly exsert; S 3 and S 4 progressively smaller and less exsert; S 5 follow S 1 −S 2 in their exsert projections; S 1 and S 2 are the longest and subequal in length, S 3 are slightly shorter, and S 4 −S 5 are similar and notably shorter than S 3. Pali forming a palar crown before S 4 (24 P 4), with their upper and inner edges slightly sinuous and scarce, small, pointed granules. Fossa moderately deep, containing a columella far from the calicular margin level; columella apparent, neat, elliptical, formed by numerous twisted ribbons, many fused. Corallum white to cream.
Remarks. The specimens are of varied sizes. In stn. V 3, they range in H from 0.80 to 3.45 cm, in GCD from 1.0 to 4.16 cm and in LCD from 0.86 to 3.38 cm (GCD: LCD= 1.08−1.23). The smallest specimen examined (GCD= 1.0 cm, stn. V 3) has 44 septa arranged in four incomplete cycles (6 S1, 6S2, 12S3, 20S 4). Another specimen with GCD= 1.59 cm (stn. V 3) has 56 septa in five incomplete cycles and 12 well developed P 4.
Caryophyllia seguenzae is a coral widely distributed in the north-eastern Atlantic, although unknown from the Mediterranean Sea (Zibrowius 1980). Most part of the records are from the Bay of Biscay (Roule 1896; Marion 1906; Zibrowius 1980; Altuna Prados 1994 a, 1994 b; Altuna 1995), including Le Danois Bank (Zibrowius 1980). Not recorded in an intensive study at suitable depths off Asturias in the Avilés Canyon system (Álvarez Claudio 1993, 1994c; Louzao et al. 2010). Not recorded from the Galicia Bank, but locally very abundant further east in some locations of the Bay of Biscay (Capbreton Canyon, Altuna 1995). The species seems to rarify southwest along the north-Iberian bathyal, or is only locally abundant.