The genus Tetilla Schmidt, 1868 is differentiated from other genera belonging to Tetillidae by a lack of porocalices and distinct cortex consisting of collagen fibers and special cortical megascleres. Approximately 50 species of Tetilla from all parts of the world’s ocean have been described (Hooper and van Soest, 2002). Three species of Tetilla from Korean waters have been reported: T. ovate, T. australis and T. koreana (Thiele, 1898; Bergquist, 1968; Rho and Sim, 1981). Specimens examined in this study were collected during SCUBA diving at a depth of 5m from Hwasun Harbor, Jejudo Island, Korea. All procedures follow the methods of Rutzler (1978). Type specimens are deposited in the Natural History Museum, Hannam University (HUNHM).

Phylum Porifera Grant, 1836

Class Demospongiae Sollas, 1885

Subclass Tetractinomorpha Levi, 1953

Order Spirophorida Bergquist and Hogg, 1969

Family Tetillidae Sollas, 1886

^1*Tetilla hwasunensis n. sp. (Figs. 1, 2)

Holotype (Por. 104), Hwasun Harbor, Jejudo Island, 2 Sep 2009, Kim SH, by SCUBA diving, at 5 m in depth, HUNHM. Paratype (Por. 104-1), collected with Holotype, HUNHM.

Globular shape with one root-like base consisting of spicules and sand, size up to 4.3×3.5×1 cm. A single oscule 5 mm in diameter, opened at center of body. Colour pink in life, beige in ethanol. Texture very compressible. Surface of body even and smooth. Skeletal structure showing radial arrangement without distinct cortex. Bundles of oxeas run from basement to the surface. Surface region densely packed with oxeas and small protriaenes in fence-like structure. Lower part of body with less spongin. Root in base with dense anatriaenes and large protriaenes mixed with sand.

Spicules. Oxeas straight or slightly curved. Anatriaenes very long and curved at tip. Protriaenes long and thin, it’s clad unequally long. Sigmaspires with fine spines.

Megascleres (㎛).

Large ？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？1,180-1,830×8-10

Small oxeas？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？600-950×4-6

Anatriaenes？？？？？？？？？？？？？？？？？？？？？？？？？？？？？rhabds 1,940-4,500×2-5

clads 15-40

Large protriaenes？？？？？？？？？？？？？？？？？？？？？rhabds 1,800-2,050×4-7

clads 35-60

Small protriaenes ？？？？？？？？？？？？？？？？？？？？？？？？？？rhabds 250-660×1-2

clads 75-100

Microscleres (μm).

Sigmaspires？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？？10-15

The species is named after the type locality, Hwasun Harbor, Jejudo Island.

T. hwasunensis n. sp. is similar to both T. serica collected from Japan (Lebwohl, 1914) and T. radiate from Brazil (Selenka, 1879) in globular shape and radial skeletal structure; however, this species is easily distinguished from T. serica by a lack of spherules as microscleres. And the new species has sigmaspires; however, T. radiate doesn’t have spicules. T. australis, reported in Korea (Rho and Sim, 1981), are covered with neumerous conules on the surface, whereas

the new species has an even surface.

Korean name: 1*화순유두해면 (신칭)