Habitat: Common sponge on cryptic habitats and coral rubble. Rarely found on exposed areas of the reef. Distribution: Caribbean wide. Natural History Notes: Eaten by Hawksbill turtles, Eretmochelys imbricata. Characteristics: Shape: Thinly encrusting (1 mm thick) forming variable sized patches (< 100 cm 2). Color: Bright vermilion red when alive, pink in ethanol, off white dry. Consistency: Compressible, but very thin. Surface: Smooth texture to the naked eye. Spicules pierce through the skin creating a microhispid appearance evident under the compound scope. Apertures: Small oscules, 0.5-1mm in diameter, often on small mounds. Skeleton: Spicules are thick (approx. 15μm in diameter, 200-350μm in length) and thin tylostyles (approx. 300 x 5 μm), straight. Microscleres are spirasters (40-50 μm). Ectosomal skeleton: a densely packed layer of microscleres 50μm in thickness, Megascleres pierce through the surface. Choanosomal skeleton: less dense than ectosome with sscending tracts of megascleres and spongin. Canals are visible, larger ones measuring 230μm in diameter. Notes: Synonyms: Thalysias coccinea (Duchassaing and Michelotti 1864). (WPD)