Body Width: 10 cm. Body Thickness: 0.8 cm. Mean live weight about 200 g to 1000 g; body thickness about 4 mm. Body: cylindrical, elongate, with rounded ends. Tegument smooth, often covered by sand, but also showing round patches lacking sand. A red toxic fluid is secreted upon rubbing the body surface vigorously. Podia on bivium sparsely distributed, ending in a small disc around 150 micrometer in diameter; podia on trivium numerous, short and stout, distributed on the radii and the interradii, their calcareous disc around 0.05 cm in diameter. Mouth: ventral, surrounded by 20 black tentacles. Anus terminal. Calcareous ring with large radial pieces and narrow interradials. Cuvierian tubules absent. Color: entirely black. Spicules: tegument with tables and rosettes; tables with circular disc showing 8 holes (4 central and 4 smaller holes in between) and s spire of 4 pillars, ending in maltese crown; rosettes small and simple, more abundant in ventral tegument; ventral podia without rods, but with pseudo-plates; dorsal podia and papillae with short rods, showing denticulate borders.