Siphonodictyon xamaycaense Pulitzer-Finali, 1986

Synonymy and References. Siphonodictyon xamaycaense Pulitzer-Finali, 1986: 164, figs. 77, 78.

Material. USNM 1229129, Carrie Bow forereef, inner slope (toward trough), lower side of platy coral rubble, 18 m; K, Ruetzler col. 14 May 1975. USNM 1229130, Curlew Bank forereef slope, lower surface of Agaricia coral plate, 21 m; C. Piantoni, col. 28 Jun 2007. USNM 1229131, Curlew Bank forereef cave, 20 m; C. Piantoni col. 2 Jul 2007. USNM 1229132, Curlew Bank forereef slope, 50–150 cm inside framework cave, ceiling, 20 m; C. Piantoni and M. Parrish col. 22 Aug 2012.

External morphology. This excavating sponge consist of tissue filling endolithic cavities connected by tunnels to epilithic, ectosomal oscular tubes and inhalant fistules (apically closed tubes). The excavations are spherical, ovoid, or (the larger ones) irregular in outline and measure from 1 x 1 x 1 cm to about 2 x 2 x 5 cm, in our specimens, and are located 0.5–2 cm below the substratum surface. They connect to the epilithic structures by more or less (2–8 mm) narrow tunnels lined by tissue. The exterior structures of small specimens are tiny hollow cylinders (exhalant tubules, 5–12 mm tall, 1.5–3 mm in diameter), some apically closed (inhalant fistules). In larger specimens they reach 4 cm in height, 1 cm in diameter (at the base, tapering toward the apical end). Specimens observed on the open reef may have tubes and fistules as big as 10 x 1.5 cm. The endolithic tissue is soft and mucous, beige in color, the external tubes are brittle and white, some with a grayish or purplish tint.

Skeleton structure. In the endolithic choanosome, oxeas are abundant but without particular orientation. In the ectosomic inhalant-exhalant structures, they form meshes or a network of tracts, with loose spicules in between.

Spicules. Oxeas are curved, with dull or rounded, some with stepped or mucronate points: 100–150 x 4–10 (131 x 6) Μm

Ecology. Excavating dead coral, on the open forereef and in caves, 18– 21 m.

Distribution. Caribbean.

Comments. This species is quite common in cryptic environments but the larger specimens, as judged from epilithic tubes and fistules, occur on the open reef, in 20– 45 m.