Siphonidium ramosum (Schmidt, 1870)

Figures 66 a–d

Leiodermatium ramosum Schmidt, 1870: 21, pl. 3 fig. 1.

Siphonidium ramosum; Schmidt 1879: 28, pl. 1 fig. 8; Van Soest & Stentoft 1988: 66, text-fig. 31; Pisera & Lévi 2002: 342, figs 6–8; Mothes & Silva 1999: figs 27–32, 42–46.

Material examined. RMNH Por. 9824, Suriname, ‘Luymes’ Guyana Shelf Expedition, station 1, 7.1667°N 53.5833°W, depth 104–130 m, bottom sandy calcarenite, 24 August 1970 .

Description. Cushion-shaped sponge (Fig. 66 a) with characteristic ‘cut-off’ fistules spread over the surface. Size of single specimen 3 x 2.5 x 2.5 cm, individual fistules 2–4 mm in diameter. Color in alcohol orange–beige. Surface overgrown by sponges, bryozoans, vermetids and serpulids. Consistency hard.

Skeleton. (Figs 66 b–c) At the surface there is a special, dense, tightly interlocking mass of knobby desmas (Fig. 66 b), overlying a more open choanosomal skeleton of rhizoclone desmas (Fig. 66 c) with smooth cladi provided with strongly tuberculated zygomes. Bundles of exotyles are arranged at right angles to and slightly protruding from the surface.

Spicules. (Figs 66 b–d) Desmas, exotyles.

Rhizoclone desmas, of the surface skeleton (Fig. 66 b) 150–200 µm diameter, tuberculated but tending to be smooth at the parts facing outwards.

Rhizoclone desmas of the choanosome (Fig. 66 c) 200–300 µm in diameter, smooth part of the cladi 30–50 µm in diameter, zygomes approximately 100 µm.

Exotyles (Figs 66 d,d1), tylostyle-like but with heads protruding outwards and rugose or irregularly spined, pointed ends occasionally wispy or bluntly rounded, in a large size range, 252– 313 –438 x 3.5– 5.3 –7.5 µm.

Distribution and ecology. Guyana Shelf, Florida, Barbados, SE Brazil, (reported also from E Atlantic and Mediterranean), hard sandy bottom at 104–439 m (previously 150–439 m).

Remarks. A widespread species in the Central West Atlantic (common at 150 m off Barbados, rare elsewhere). It is reported along the SE Brazilian coast at 30°S and also—if the same species—at greater depths in the Azores and the Mediterranean. Size of the exotyles varies among the localities, but the holotype (measurements of Mothes & Silva 1999, table 1) and the present measurements are in the same range. The Azores specimen described by Topsent (1904) had exotyles of 800– 1000 x 4–6 µm, distinctly longer than the known Caribbean measurements. Further research must establish if S. ramosum may have been erroneously reported from the East Atlantic .