Clathria (Thalysias) venosa (Alcolado, 1984) (Figure 2 a) Synonymy and References. Microciona venosa Alcolado, 1984: 6, fig. 4A. Material. USNM 1229019, Carrie Bow Cay, reef flat East, 0.5 m, underside of coral plate; K. Ruetzler col. 1 May 1974. USNM 1229020, 1229021 Carrie Bow Cay, under concrete dock; K. Ruetzler col. 12 May 1978. USNM 1229022, Carrie Bow Cay, South reef, lower surface of coral slab, 1 m; K. Ruetzler col. 9 Jan 1988. USNM 1191357, Carrie Bow south barrier back reef, underside of platy coral rubble, 0.5 m; K. Ruetzler col. 6 Mar 2006. USNM 1191358, Carrie Bow Cay, under CBC concrete dock, 1 m; K. Ruetzler col. 3 Jul 2007. External morphology. Thin, soft and somewhat mucous crusts, 25–40 cm 2, with vein-like canals leading toward small oscula (1mm, fully contracted in alcohol). Live color gray to yellow-orange on the surface, red below. Skeleton structure. Megasclere tracts (subtylostyles echinated by small acanthostyles) extending from the substrate toward the surface; brushes of small subtylostyles protruding from ectosome. Very thin toxas (toxashaped raphids) and chelas throughout the tissue. Spicules. Subtylostyles I, some with minute spines (only seen by SEM) on the heads: 190–450 x 3–7 (274 x 4) Μm; subtylostyles II, some are styles: 60–150 x 1–3 (138 x 2) Μm; acanthostyles: 43– 60 x 3–8 (48 x 5) Μm; toxas: 30–325 x <1 (164 x <1) Μm; palmate isochelas, 9–15 (13) Μm long, some of them twisted. Ecology. Found under a concrete dock in the lagoon and on the lower surface of dead Acropora palmata plates in a wave-exposed exposed zone of the barrier-reef crest, in 0.5 –1 m depth. Distribution. Gulf of Mexico and Caribbean. Comments. Chelae are rare or absent in some specimens.

Published as part of Rützler, Klaus, Piantoni, Carla, Van, Rob W. M. & Díaz, Cristina, 2014, Diversity of sponges (Porifera) from cryptic habitats on the Belize barrier reef near Carrie Bow Cay, pp. 1-129 in Zootaxa 3805 (1) on pages 62-63, DOI: 10.11646/zootaxa.3805.1.1, http://zenodo.org/record/249983