A newly recorded species, Nereiphylla hera Kato and Mawatari, 1999 which was originally described from northern Japan, was collected from East Sea in Korea. Our Korean materials of N. hera are distinguished from it congeners by the following characteristics that agree well with the original description of the species: the tentacular cirri are flat and spatulate with a narrow and distinct tip, reaching to segment 4-6, and boarder than their cirrophores; the parapodia possess elongated dorsal cirri. We provide a key for distinguishing the species of genus Nereiphylla from Korean waters.

A newly recorded glycerid polychaete collected from mud of the tidal flat in the southwestern coast of Korea is identified as Glycera fallax Quatrefages, 1850 based on the morphologies of papaillae and ailerons on proboscis, parapodial postsetal lobes, and branchiae. In this paper, we provide a detailed description and illustration of Korean materials of this species and a key to the species of the genus Glycera from Korean waters.

A harpacticoid species, Paramphiascella fulvofasciata Rosenfield and Coull, 1974, belonging to Miraciidae Dana, 1846 is newly reported from Korean waters. The species is mostly related with P. pacifica Vervoort, 1962, however, it is easily distinguished by the typical structure of male P2 in having 1 large spine and 2 setae on P2 enp-2. Korean materials represented some discrepancies from the original description of P. fulvofasciata in the detailed structures of mouth parts. The present study is a first record of the genus Paramphiascella Lang, 1944 from Korean waters.

The genus Halectinosoma Vervoort, 1962 is first reported from Korean waters by the discovery of H. perforatum Itô, 1981. This species, previously recorded only from Japan, is collected from the sandy beach on the south coast of Korea, and is well distinguished from other congeners by the combination of following morphological characteristics: the elongate caudal ramus; the remarkably bilobated exopod of female P5; the small innermost seta on the distal margin of female P5 exopod; the presence of three setae on the distal exopodal segment in P4; and the presence of scale-like spinules on the ventral surfaces of urosomite. We herein provide detailed description and illustrations of this species.

Newly recorded cyproideid species of the genus Terepeltopes was collected from Korean waters. The monotyptic genus Terepeltopes erected with T. dolichorhunia Hirayama, 1983 was only known to be found at West Kyushu, Japan. In this study, the family Cyproideidae Barnard, 1974 is first recorded from Korea by the discovery of T. dolichorhunia, and we provide description and illustrations of this species.

Despite the worldwide distributions of genus Lepidepecreum and the previous reports from China and Japan, this genus has not yet been recorded in Korean waters. In this study, Korean materials of lysianassid amphipods are assigned readily to the genus Lepidepecreum and identified as L. vitjazi Gurjanova, 1962 based on the following features: well-developed dorsal keels of the pleonite 3 and urosimite 1; unconcaved palmer margin of ganthopod 1; hooked locking spines of propodus on pereopods 3 and 4; and the shape of coxa 4. We also provide the description and illustrations of this species.

Two newly recorded opheliid polychaetes, Armandia amakusaensis Saito, Tamaki and Imajima, 2000 and Polyophthalmus qingdaoensis Purschke, Ding and Müller, 1995, from Korean waters are reported with the descriptions and illustrations. Armandia amakusaensis can be clearly distinguished from its congeners by the following characteristics: the prostomium has 2 or 3 subdermal eyespots; total number of setigers are 29; the branchiae are present on the setigers from the setiger 2 to the second or third from the last setiger; the lateral eyespots beginning from the setiger 7 are composed of 11 pairs; the anal funnel has 8~11 papillae and a long cirrus. Polyophthalmus qingdaoensis has the distinguishable characteristics from its relatives as follows: the prostomium has a brain bearing dark pigment-spots; the lateral eyespots are distinct; the body has only dark pigment-streaks on dorsal side. We also provide the keys for distinguishing the species of the genera Armandia and Polyophthalmus from Korean waters.

The goniadid species, Glycinde bonhourei Gravier, 1904, is newly reported with the description and illustration from Korean waters. Our Korean materials of G. bonhourei have the following characteristics that are generally known as distinctive features from its congeners: the area II-1 on proboscis possesses unidentate papillae bearing broad base; the area IV on proboscis bears the papillae of duct’s foot-shaped with rounded teeth; the area V on proboscis has straightly conical papillae bearing slightly bifid tip; 4-16 micrognaths are arranged on the dorsal side; all parapodia have one neuropodial presetal lobe; uniramous parapodia are present on 19-26 anterior segments. As a result of the present study, the genus Glycinde is newly reported from Korean waters.