Cyclopina curtijejusp. nov. is described from two females from Jeju (off South Coast); it is possibly closely related to C. smirnovi Herbst, 1982, but the latter is known from a single male from the Russian Far East. Cyclopina widosp. nov. is described from both sexes from Wido (West Coast), and shows numerous reductions in segmentation and armature of appendages, most of them probably a consequence of its diminutive size. A table of 26 discrete and continuous characters commonly used in the taxonomy of this group is provided for 48 valid species and subspecies of Cyclopina.The number of described species of the genus Terebellides Sars, 1835 (Annelida, Trichobranchidae) has greatly increased in the last years, particularly in the North East Atlantic. In this context, this paper deals with several putative species recently delineated by molecular means within a well delimited clade of Terebellides. Species are characterised here by a combination of morphological characters, and a complementary nucleotide diagnostic approach. Three species were identified as the nominal species T. stroemii Sars, 1835, T. bigeniculatus Parapar, Moreira & Helgason, 2011 and T. europaeaLavesque et al., 2019. Five species are described as new T. bakkenisp. nov., T. kongsrudisp. nov., T. norvegicasp. nov., T. ronningaesp. nov. and T. scoticasp. nov. The distinctive morphological characters refer to the branchial shape, absence or presence of papillae on lamellae of anterior margin of branchial dorsal lobes, absence or presence of ciliated papillae dorsal to thoracic notopodia, geniculate chaetae in one or two chaetigers, and the morphology of thoracic and abdominal uncini teeth. Furthermore, the description of T. bigeniculatus is revised and complemented after examination of type specimens. An updated identification key to all species of the genus in NE Atlantic and a proposal of a classification of different types of abdominal uncini to be used in taxonomy are also included.A new species of the genus Goniurosaurus is described based on three specimens collected from a limestone cave in Huaiji County, Guangdong Province, China. Based on molecular phylogenetic analyses, the new species is nested within the Goniurosaurus yingdeensis species group. However, morphological analyses cannot ascribe it to any known species of that group. It is distinguished from the other three species in the group by a combination of the following characters scales around midbody 121-128; dorsal tubercle rows at midbody 16-17; presence of 10-11 precloacal pores in males, and absent in females; nuchal loop and body bands immaculate, without black spots; iris orange, gradually darker on both sides. The discovery of yet another limestone-adapted species of Goniurosaurus in Guangdong Province underscores a growing body of evidence for the high biodiversity of limestone habitats and brings into sharp focus the urgent need for their conservation.This is the first record of the genus Typhlocolenis Hoshina, 2008 (Coleoptera, Leiodidae, Leiodinae, Pseudoliodini) in South Korea. Two new Korean species are described, under the names T. sillaensissp. nov. and T. jejudoensissp. nov. As a result of this study, the number of Typhlocolenis species is now five. A key to the species of the genus is provided.A new whitefly species, Aleuroclava schimae Wang, sp. nov. infesting leaves of Schima superba (Parietales, Theaceae) is described and illustrated from Zhejiang, China. Puparia of the new species are elliptical, broad at the transverse molting suture region and broadly truncate posteriorly. Thoracic and caudal tracheal pores are discernible. In life, the puparia are covered by a thin layer of white wax.Pseudopoda taibaischana Jäger, 2001 (Sparassidae) is redescribed based on new material from the type locality in Taibaishan Nation Forest Park of Shaanxi Province, China. The female is described and illustrated for the first time, and a redescription is provided for the male.The cerithioid Supplanaxis nucleus (Bruguière, 1789) is widespread in the Caribbean, where it lives in often dense aggregates on hard surfaces in the middle-high intertidal. Molecular evidence shows that it comprises two species that are in fact morphologically diagnosable. We fix the nomenclature of Supplanaxis nucleus by designating a sequenced neotype from Bruguière's historical locality of Barbados, and identify the second, cryptic species as S. nancyae (Petuch, 2013). The two live syntopically across the Caribbean and form a closely related species group with the Panamic S. planicostatus (G.B. Sowerby I, 1825). Planaxis nucleola Mörch, 1876, described from St Croix, in the Virgin Islands, never again recorded in the literature but listed as a synonym of S. nucleus in taxonomic authority lists, is recognized as a valid species of Hinea Gray, 1847. Proplanaxis Thiele, 1929 and Supplanaxis Thiele, 1929, are synonyms and the latter is given precedence over the former.In this study, Stenothyra glabra belonging to the truncatelloid family Stenothyridae is redescribed using morphological characters from the shell, operculum, and radula. The species is distinguished from other species in the group by its shell without spotted spiral lines and by its dome-shaped, mostly smooth, protoconch with some pits. Together with the morphological description, the complete mitogenome for the species is provided, which fill a knowledge gap in Stenothyridae. The mitogenome of S. glabra is 15,830 bp in length and has a circular structure. It contains 37 genes 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs), and 13 protein-encoding genes (PCGs). The overall A+T content of the mitogenome is 68.9%. Molecular phylogenetic analysis and COI sequence divergence separate S. glabra from its congeners and show that S. glabra and S. cf. divalis form a sister clade.The lamprey genus Lethenteron Creaser & Hubbs, 1922 is widespread across Eurasia and North America, but the number and distribution of its constituent species is not firmly established. After a morphological examination of extant type material of the currently recognized species and their synonyms, Lethenteron mitsukurii (Hatta, 1901) is resurrected with Le. Zasocitinib in vivo matsubarai Vladykov & Kott, 1978 as its junior synonym. Amongst nonparasitic species Le. reissneri (Dybowski, 1869) and Le. mitsukurii are confirmed as present in Japan and the former is also present on Sakhalin. An in-depth study of large samples of nonparasitic lamprey adults from Japan and Sakhalin Island is needed to determine whether the lower trunk myomere ( less then 66) individuals from these areas represent one or more undescribed species, or Le. mitsukurii, or Le. reissneri, or a mixture of these three alternatives. The material from the Anadyr Estuary identified by Berg (1931, 1948) as Lampetra japonica kessleri has been re-identified as Le. camtschaticum and there is no evidence that Le.