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Farrea bowerbanki n. sp. Boury-Esnault, Vacelet & Chevaldonné Type-specimen. Sample VAL2-ACH-P15_ECH01. MNHN-HJV-03 Type-locality. Valinco Canyon, SW Corsica (Western Mediterranean), 383 m, 41.66148N / 8.7953E, 31/07/ 2014. Comparative material. Slides from specimens of the Ibero-Morrocan Gulf (BALGIM Cruise, 1984, Stn CP91-13, 34.3675N – 7.417W, 945 m). External morphology. Several specimens were observed on ROV pictures and videos or by direct observations from the manned submersible ‘Remora 2000’ (Comex) in 2009, 2010, 2014 and 2016 (Fig. 1, 2 and 4, Table 3). A complete specimen, designated as holotype, has been collected in 2014. The holotype (Fig. 2 A, 2C) is 15 cm high, with a diameter of about 20 cm at its widest part. The body is formed by a branching and anastomosing system of tubes attached to the rocky substrate by a small basal plate, 2 cm in diameter. Two main tubes, 2 cm in diameter, arising from the basal plate, divide and merge several times, with distally infundibular openings 5–8 cm wide. The shape of these openings is reminiscent of a flower corolla. The thickness of the tube wall is about 1–2 mm. Color in life is white, with the basal plate and a short common basal part of the tubes, deep grey. The sponge is very fragile, and several parts of the tubes are broken on the preserved holotype which was very difficult to collect in a good state of preservation by the ROV. The other specimens observed, such as shown in Figures 2 B, 4A, 4B and 4D, have the same general shape, varying in size from a few centimeters to 40 cm. Several observed specimens were composed of a white living part and of a dead skeleton, colored in grey due to the deposit of mud. Skeleton. The skeleton framework is a typical farreoid dictyonal type with smooth beams and spined spurs (Fig. 2 D, 2F). Dictyonalia are formed in more than one layer. The meshes are mostly rectangular, sometimes square or triangular (Fig. 2 E), with dictyonal beams 168–430/35–50 µm in size. The spurs are 90–210 µm in length, always spined and most often curved (Fig. 2 F).

Tretodictyum reiswigi n. sp. Boury-Esnault, Vacelet & Chevaldonné Type-specimen. Sample VAL2-ACH-P15-ECH02. MNHN-HJV-04, Type-locality. Valinco Canyon (Western Mediterranean) 41.662N / 8.795E, 397 m, 31/07/2014. Other material (available in SME collection): Sample CS-ACH-P03- ECH 06 b, a small fragment encrusting a brachiopod shell, Cassidaigne canyon (W Mediterranean) 43.047N / 5.397E, 370 m, 28/10/2009. Sample VAL- ACH-P12- ECH 01, small fragments, Valinco Canyon, Corsica, 41.663N / 8.795E, 444 m, 24/08/2010. Sample from CYLYCE cruise, dive 12 of Cyana submersible, fragments of two tubes, Ile Rousse Canyon, NW Corsica, 42.833N / 8.953E, 320 m, 25/05/1997, Slides from specimens of BALGIM Cruise, R / V Cryos, Alboran Sea, Station CP 135-168, 35.435N / -4.301W and DR152–257, 35.935N/-5.569W, 390–560m, May–June 1984. External morphology. The sponge is formed by several tubes more or less coalescent, expanding from a narrower base of attachment to the substrate. The tubes are most often arranged in a single or a double line (Fig. 3), with each line formed by up to 12 tubes. The maximum size estimated from ROV images is ca 15 x 7 x 5 cm, with tubes either entirely joined or free for up to 5 cm. The tubes are 1–2.2 cm in diameter with a central canal 0.55–0.65 cm in diameter. The wall of the tubes is ca 3 mm thick. The surface is pierced by numerous small depressions. The color is pure white in living or freshly dead specimens, grey in dead skeletons due to sediment deposits. Specimens with both living parts and dead skeletons have often been observed (Fig. 3 B). The consistency is hard, but the sponge is easily broken. Numerous observations of sponges with very similar external characters have been made between 199 and 632 m depth from submersible and ROV dives, for examples Fig. 3 A, 3B; Fig. 4 B, 4C, 4D (Table 3). Their identification to the same species is made with great confidence. Skeleton. The main skeleton is a dictyonal framework of square meshes with 200–300 µm sides and beams 30–60 µm thick, with tubercles arranged in rows. Megascleres are dermal and parenchymal hexactins. Strongyloscopules are present in dermal and atrial surfaces. Microscleres are oxyhexactins and two types of hexasters.