Total length to 47 cm, common to 28 cm. Head, body and fins are generally dark brown. The skin is warty, scaleless and often covered in a short coat of filamentous algae. Thirteen sharp dorsal spines are each contained in a thick sheath of skin. The head has deep pits and grooves. The eyes are small and situated on a raised bony structure. The pectoral fins are enlarged and fleshy.