Caminus jejuensis n. sp was collected from depth of 20 m at Geomeunyeo, Seogwipo, Jejudo Island by a SCUBA diving from April 2004 to December 2008. This new species is similar to C. chinensis from China in the composition of spicules except for the spherasters and they differ in spicule size and growth form. This species has longer orthotriaenes and spherules, smaller sterrasters and oxyasters than those of C. chinensis . This species also has many spherasters in choanosome, but C. chinensis lacks. Morever, the new species is a massive shape with wrinkles, whereas C. chinensis is a club shape with smooth surface. Description and figures of the new species are provided. The genus Caminus within family Geodiidae has a single article oscule at the top of the sponge body, and sievelike inhalant pores. The megascleres are consisted of oxeas, strongyles and orthoreiaenes. And also, the microscleres composed of subspherical sterrasters and spherules in cortex and oxyasters in choanosome (Hooper and van Soest, 2002). Up to now, 5 species have been reported in the world (Schmidt, 1862; Sollas, 1886; Lindgren, 1897; Tanita, 1969; Pulitzer- Finali, 1996). Among them, only one species has been reported from the Korean waters (Sim and Byeon, 1991). Specimens were collected from depth of 20 m at Jejudo Island by a SCUBA diving from April 2004 to December 2008. They were preserved in 95% ethanol and then deposited in the Natural History Museum of Hannam University (HUNHM). The colour and texture were described before preservation. Identification was based on the morphological characteristics, skeletal structure, shape and size of spicules. Skeletal structure and spicules were examined by using microscopy and scanning electron microscopy (SEM). Length and width of 20 spicules were measured for each spicule type. Procedure of dissociated spicules followed Rützler (1978). Type specimen. Korea: Holotype (Por. 108), Geomeunyeo, Seogwipo, Jejudo Island, 16 Apr 2004, Lee KJ, by SCUBA diving at 20 m deep, HUNHN. Paratype (Por. 108-1, 108-2), Geomeunyeo, Seogwipo, Jejudo Island, 19 Dec 2008, Kim BI, by SCUBA diving at 20 m deep, HUNHM. Description. Massive shape with thick wrinkles, sized up to 5×4×3.5 cm. Oscule 1-3 mm diameters, rarely scattered. Surface wrinkles. Texture very hard, due to a layer of sterrasters and spherules. Colour khaki in life, gradually changed to brown in alcohol. Cortex 1 mm thick, easily separated from choanosome, densely packed with sterrasters and spherules. Choanosome arranged with oxeas and orthotriaenes. Clads of orthotriaenes faced to cortex and rhabds faced inwards. Oxyasters and spherasters scattered in sponge body. Spicules. Megascleres oxeas and orthotriaenes. Microscle- res sterrasters, spherasters, oxyasters and spherules. Sterrasters round shaped with flat asterose and horn shaped projections at surface. Oxyasters and oxyspherasters spines at ray. Spherules spines on surface. Etymology. This species is named after the type locality, Jejudo Island, Korea. Remarks. This new species is similar to Caminus chinensis from China (Lindgren, 1897) in the composition of spicules except for the spherasters. They differ in the spicule size and growth form. This species has longer orthotriaenes and spherules, smaller sterrasters and oxyasters than those of C. chinensis . This species also has many spherasters in choanosome, but C. chinensis lacks ( Table 1 ). Morever, the new species is a massive shape with wrinkles, whereas C. chinensis is a club shape with smooth surface.