Two new marine sponges, Haliclona ( Haliclona ) tonggumiensis n. sp. and H. ( Reniera ) sinyeoensis n. sp., in the family Chalinidae were collected from Ulleungdo Island and Gageodo Island, Korea from 2007 to 2009. Haliclona ( Haliclona ) tonggumiensis n. sp. is similar to H. ( H. ) simulans (Johnston, 1842) in shape, but the former differs in its ectosomal skeleton structure and spicules’ shape and size. The ectosomal skeleton of H. ( H. ) tonggumiensis n. sp. is absent, but that of H. ( H. ) simulans is very regularly arranged, and has tangential reticulation with oxea. The spicule shape of H. ( H. ) tonggumiensis n. sp. is slender, but that of H. ( H. ) simulans is short and cigar-shape. The new species have two sizes of oxea, but H. ( H. ) simulans has one size of oxea. Haliclona ( Reniera ) sinyeoensis n. sp. resembles H. ( R. ) tubifera (George and Wilson, 1919) in the growth form and choanosomal skeleton structure. However, the new species has two kinds of oxea in size, but H. ( R. ) tubifera has only one size. The family Chalinidae Gray, 1867 which is the largest family of the order Haplosclerida (De Weerdt, 1986) has worldwide distribution and is taxonomically most complicated, because of their scarcity, simplicity and sometimes high variability of taxonomic characters (De Weerdt, 2000). This family consists of four genera, including Dendroxea , Chalinula , Cladocroce , and Haliclona . According to the World Porifera Database (WPD) (Van Soest et al., 2012), 197 species of the genus Haliclona are reported from the world. The genus Haliclona is subdivided into six subgenera, Gellius , Halichoclona , Haliclona , Reniera , Rhizoniera , and Soestella (Hooper and Van Soest, 2002). According to the definition of De Weedrt (2000) for the genus Haliclona , the choanosomal skeleton of subgenus Haliclona is regularly reticulated like a ladder by uni-paucispicular primary lines and is regularly connected by unispicular secondary lines. Oxeas are short, rather robust, fusiform or with acerated points. The choanosomal skeleton of subgenus Reniera consists of a delicate, regular, unispicular and isotropic reticulation. Oxeas are frequently blunt-pointed or strongylote. Twenty nine species of genus Haliclona have been reported from Korean waters (Kim et al., 1968; Rho and Lee, 1976; Sim, 1981; Rho and Yang, 1983; Sim and Kim, 1988, 2002; Sim and Byeon, 1989; Sim et al., 1992; Sim and Lee, 1997; Kim and Sim, 2004; Kang and Sim, 2007, Jeon and Sim, 2008). Among them, one species of subgenus Haliclona and one species of subgenus Reniera have been reported (Kang and Sim, 2007 in WPD). Sponges were collected by SCUBA diving from Gageodo Island and Ulleungdo Island, Korea, from 2007 to 2009. Specimens were fixed in 95% or 99.9% ethanol. Spicules were observed under a light microscope (Axioskop II; Carl Zeiss, Jena, Germany). Identification was made on the basis of external features of the sponges, including growth form, skeletal structure, and spicule size and form of spicules. For the observation of the choanosomal skeletal structure, thin free-hand sections were made with specimens hardened in alcohol using a surgical blade. Spicules were prepared by dissolving a piece of sponge in sodium hypochlorite and were examined under a scanning electron microscope (HITACHI S-3500) (Rützler, 1978; Hooper, 1996). Holotypes of two new species have been deposited in the National Institute of Biological Resources (NIBR), Incheon, Korea. Paratypes have been deposited in the National Science Museum of Korea (NSMK) and the Natural History Museum of Hannam University (HUNHM), Daejeon, Korea. The classification used here follows the Systema Porifera (Hooper and Van Soest, 2002). Material examined. Holotype, Korea: Gyeongsanbuk-do, Ulleung-gun, Seo-myeon, Namyang-ri, Tonggumi, 9 Sep 2009, SCUBA diving, 3 m depth, Kang DW, Rho HS, deposited in the NIBR (NIBRIV0000259987). Paratype are deposited in NSMK (NSMK-POR-0000004) and in HUNHM (por. 110). Description. Growth form thinly encrusting, 0.1 cm thickness and 5 cm width, with small circular oscules. Oscules 0.1-0.2 cm in diameter, scattered on surface. Color pink in life gradually changing to ivory in alcohol. Texture soft, fragile and compressible. Surface smooth and even. Spongin moderate to abundant, yellowish and clearly visible. Skeletal structure on surface reticularly arranged by unispicular oxea under membrane with pores, and single oxea slightly hispid to outer surface. Skeleton in thin surface membrane absent. Choanosomal skeleton composed of ladder-like reticulation by uni-paucispicular primary lines and regularly connected by unispicular secondary lines. Spicules composed of two type of oxea and no microscleres. Thick oxea approximately 90-110×3.5-5 μm in size. Thin oxea approximately 60-70 ×1-1.5 μm in size. Fusiform thick oxeas, straight to slightly arched or bent at middle. Etymology. This species is named after the type locality, Tonggumi, Ulleungdo Island, Korea. Remarks. Haliclona ( Haliclona ) tonggumiensis n. sp. is similar to H. ( H. ) simulans (Johnston, 1842) in shape, but the former differs in its ectosomal skeleton structure and spicule shape and size. The ectosomal skeleton of H. ( H. ) tonggumiensis n. sp. is absent, but that of H. ( H. ) simulans is very regularly arranged, and has tangential reticulation with oxea (see De Weerdt, 1986). The spicule shape of H. ( H. ) tonggumiensis n. sp. is slender but that of H. ( H. ) simulans is short and cigar-shape. The new species have two sizes of oxea but H. ( H. ) simulans has one size of oxea. Material examined. Holotype, Korea: Jeollanam-do, Sinan-gun, Heuksan-myeon, Gageodo-ri, Sinyeo, 19 Jul 2007, SCUBA 20 m depth, Kim HS, deposited in the NIBR (NIBRIV 0000259988). Paratype (por. 111), deposited in the HUNHM. Description. Cushion-shaped, with several volcano- or chimney- shaped oscular elevations up to 1.5-4 cm high. Up to 7 cm width, 5.5 cm height and 0.6-1.5 cm thickness. Oscules 0.4-1.5 cm in diameter, opened at top of chimney. Color purple and pink in life gradually changing to ivory in alcohol. Texture soft compressible and fragile. Surface smooth, even. Ectosomal skeleton composed of unispicular and isotropic reticulation. Spongin appear at node of spicule. Choanosomal skeleton composed of very regular, ladder-like reticulation, and without clear distinction between primary and secondary lines. Spicules composed of oxeas of two kinds in size, without microscleres. Thick oxeas approximately 130-150×5-8 μm and thin oxeas approximately 90-115×2.5-4 μm in size. Etymology. This species is named after the type locality, Sinyeo, Gageodo Island, Korea. Remark. Haliclona ( Reniera ) sinyeoenesis n. sp. resemble H. ( R. ) tubifera (George and Wilson, 1919) (see De Weerdt, 2000) in their growth form, shape and choanosomal skeleton. Also, oscules open at the top of each tube. However, the new species has two sizes of oxea, but H. ( R. ) tubifera has only one size.