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A harpacticoid copepod, Microarthridion littorale (Poppe, 1881), is newly recorded in Korea. Microarthridion species can be distinguished from each other by a combination of the number of the antennular segment, the number of the seta on the antennary exopod, and the armature of the thoracopod legs. Korean materials examined coincide well with M. littorale on these well-known characteristics. However, there are some minor differences in the ornamentations of the maxilliped and swimming legs. The specimens show additional sexual dimorphisms in the setae on enp-3 of P1 and exp-3 of P2-P4. Morphological diversity of so-called M. littorale is also discussed here with detailed features.

Since the pioneering works of the Norwegian biologist G.O. Sars, little attention has been given to the freshwater harpacticoids in Norway. The prime purpose of this paper is to present the state of current knowledge about the Norwegian freshwater harpacticoid fauna based on all known published and unpublished literature and archive material. We highlight the contribution of G.O. Sars to the knowledge of this group by presenting his remaining unpublished archive material. We present two Norwegian species checklists – one for freshwater harpacticoids (16 species) and another for freshwater-associated/brackish-water harpacticoids (nine species). Four of the freshwater harpacticoid species are described by G.O. Sars. Original unpublished plates with drawings of those species are included in the paper. In addition, an overview of species distributions throughout the country is given.

Microarthridion littorale (Poppe, 1881) References and records from Norway Tachidius littoralis Poppe, 1881 ��� Scott (1903): 11. Scott (1903) reported this species from the fjord Bogfjorden, Northern Norway, together with T. discipes. He considered M. littorale to be a more brackish-water species than T. discipes., Published as part of Dimante-Deimantovica, I., Jensen, T. C. & Walseng, B., 2016, Freshwater harpacticoids (Crustacea: Copepoda: Harpacticoida) in Norway ��� a comprehensive contribution from G. O. Sars, and a provisional checklist, pp. 1773-1795 in Journal of Natural History 50 (29) on page 16, DOI: 10.1080/00222933.2016.1159348, http://zenodo.org/record/269019

Geeopsis longicornis (Olofsson, 1917) References and records from Norway Tachidius longicornis n. sp. ��� Olofsson (1917): 34 ��� 35, type locality ��� Svalbard archipelago, several record areas given (from fresh water ��� Advent Bay, Esmark Glacier, Crednermorenen (moraine) and from brackish water ��� at Green Harbour, Billen Bay). Tachidius longicornis Olofsson (1917) ��� Olofsson (1918): 183 ��� 646. Olofsson (1917) considered T. longicornis to be very close to G. incisipes (Klie, 1913) ��� two species distinguished by their size and the morphology of the antenna. Later T. longicornis was considered to be a synonym of G. incisipes (Gurney 1932; Lang 1948). However, the species was reinstated as a valid species and placed in the genus Geeopsis by Huys (2009) as G. longicornis (Olofsson 1917) comb. nov. Olofsson (1918) found it from a brackish lagoon near Nordenskiold Glacier. The latter habitat consists of a shallow inner part with slowly running fresh water from the lowlands. Samples were taken from this part. In the lagoon ��� s outer part, water mixes with the salty water of the fjord and the proprotion of salt and fresh water changes with the tides. Another sampling locality, Lake Reliktsee (today, Vallunden), located in Crednermorenen (moraine), is connected to the sea by a channel. The tide flows in and out through the channel and therefore the water is salty (Kristensen et al. 2008). Still, Olofsson (1918) clearly indicated that he found Tachidius species in pure fresh water and suggested that this is a relict species that probably had been passively spread from northern Europe to Svalbard in later post-glacial time., Published as part of Dimante-Deimantovica, I., Jensen, T. C. & Walseng, B., 2016, Freshwater harpacticoids (Crustacea: Copepoda: Harpacticoida) in Norway ��� a comprehensive contribution from G. O. Sars, and a provisional checklist, pp. 1773-1795 in Journal of Natural History 50 (29) on page 15, DOI: 10.1080/00222933.2016.1159348, http://zenodo.org/record/269019

Tachidius discipes Giesbrecht, 1881 References and records from Norway Tachidius brevicornis (M��ller), Lilljeborg, 1853 ��� Boeck (1865): 257; Sars (1911): 328 ��� 330; Brehm (1917): 609 ��� 623. Trachidius brevicornis, Lilljeborg, 1853 ��� Sars (1863 b): 54. Tachidius arcticus sp. nov. ��� Olofsson (1917): 36. Tachidius spitzbergiensis sp. nov. ��� Olofsson (1917): 32 ��� 34. Tachidius spitzbergiensis Olofsson (1917) ��� Olofsson (1918): 183 ��� 646. Tachidius discipes Giesbrecht, 1881 ��� Scott (1903): 10 ��� 11. Olofsson (1917, 1918) considered T. spitzbergiensis a distinct, valid species, morphologically very close to T. discipes but still clearly distinguishable. Olofsson (1917, 1918) recorded it from freshwater habitats in the Advent Bay and from brackish-water habitats at Billen Bay and a brackish lagoon near Nordenskiold Glacier (Svalbard, Spitsbergen). The description of T. arcticus by Olofsson (1917) is based on material consisting of a single male specimen found in a brackish-water habitat at Green Harbour, Svalbard. This species is also considered a junior subjective synonym of T. discipes. This species was recorded from Spitsbergen (Brehm 1917), but without further indications about the exact locality. Sars (1863 b, 1911) reported this species from the Norwegian mainland, a shallow creek of the Oslofjord and brackish waters in many other places on the South and West coasts of Norway. This species seems to be tolerant of a wide range of salinity and is reported from Norway (marine habitat) by several other authors ��� Oslofjord (Boeck 1865), Bogfjord ��� Northern Norway (Scott 1903)., Published as part of Dimante-Deimantovica, I., Jensen, T. C. & Walseng, B., 2016, Freshwater harpacticoids (Crustacea: Copepoda: Harpacticoida) in Norway ��� a comprehensive contribution from G. O. Sars, and a provisional checklist, pp. 1773-1795 in Journal of Natural History 50 (29) on page 16, DOI: 10.1080/00222933.2016.1159348, http://zenodo.org/record/269019

Two new harpacticoid species belonging to the genera Microarthridion Lang, 1944 (Tachidiidae) and Nitocra Boeck, 1864 (Ameiridae) are recorded from underground caves in the karst area of Ninh Binh Province, North Vietnam. Microarthridion thanhi n. sp. is distinguished from congeneric species by the number of setae on the antennary exopod, the structure of leg 5 in both sexes, and the finger-like process modified from an outer distal pinnate seta of the third endopodal segment of leg 2 in the male. Nitocra vietnamensis n. sp. has the character combination of six setae on the ellipsoidal exopod of leg 5 in both sexes, the first endopodal segment of leg 1 shorter than the whole exopod, the seta/spine armature of an inner seta of P2-P4 enp-1 and four elements on P2 enp-3, and the reduction of the proximal endite to a seta on the maxillary syncoxa.

Four harpacticoid species belonging to the family Tachidiidae are reported from the coastal waters and salt marshes in South Korea: Tachidius discipes Giesbrecht, 1881, Neotachidius parvus Huys, Ohtsuka, Conroy-Dalton and Kikuchi, 2005, Microarthridion litospinatus Shen and Tai, 1973 and Geeopsis incisipes(Klie, 1913). The latter two species and genera are new to Korean fauna. The previous record of T. discipes reported by Song and Chang(1995)from Korea is affirmed by the finding of male specimens. Microarthridion litospinatus is first known outside the type locality, and redescribed herein in detail. A key to the five species and four genera of the family Tachidiidae hitherto known from South Korea is presented.

GENUS NEOTACHIDIUS SHEN & TAI, 1963 GRAD.NOV. Diagnosis: Tachidiidae. Rostrum elongate, delimited at base. Paired lateral integumental windows on P5- bearing somite present. Genital and first abdominal somites fused in ♀ original segmentation marked by transverse surface ridge dorsally and laterally; midventral copulatory pore not isolated from gonopores. Anal operculum spinulose. Caudal ramus setae IV ��� V well developed and pinnate. Sexual dimorphism in antennule, P2 endopod, P3 exopod, P5, P6, urosomal ornamentation and segmentation. Antennule with numerous pinnate setae/spines; 7- segmented in both sexes; chirocer in ♂, with aesthetascs on segments 4, 6 and 7; segment 5 in ♂ with spinous outgrowth. Antenna with (indistinctly) 2-segmented exopod; exp-1 with one seta, exp-2 with one lateral and two apical setae; lateral endopodal spine proximally displaced. Mandible with two setae on basis, five setae on exopod and three lateral and nine apical setae on endopod. Maxillule with four setae and one geniculate spine on coxa, and six elements on basis; exopod represented by one seta, endopod 1-segmented with three setae. Maxillary syncoxa with enditic formula [4,3,3]; allobasis with three accessory setae; endopod indistinctly 2-segmented with one geniculate spine and five setae. Maxilliped with two accessory setae on endopod; claw minutely pinnate. P1���P4 with 3-segmented rami; enp-1 of normal size and with inner seta. P1 exp-3 with two outer spines, enp-3 with one inner seta. P3 enp-3 with five setae/ spines. P4 enp-2 with one inner seta. Armature formula as follows: Exopod Endopod P1 0.1.122 1.1.121 P2 1.1.222 1.2.221 P3 1.1.222 1.2.221 P4 1.1.122 1.1.221 P 2 ♂ enp-2 with outwardly directed spinous apophysis; enp-3 small, anterior surface with transverse spinular comb concealing tip of enp-2 apophysis, outer spine reduced in size, outer distal seta rudimentary and fused to segment, inner setae well developed. P3 exopod ♂ longer than in ♀ with exp-3 often bent inwards; inner setae of exp-1 and -2 smaller than in ♀ inner distal seta of exp-3 vestigial. P 5 ♀ with outer concavity, separating outer lobe from distal portion; outer lobe with basal plumose seta and pinnate spine; distal portion with plumose seta flanked by strong pinnate spines around apex, and two (endopodal) pinnate spines along inner margin. P 5 ♂ medially fused; each with three pinnate spines and two setae. P 6 ♀ represented by opercula closing off common genital slit, each with one seta. P 6 ♂ symmetrical; each member with two pinnate spines and naked outer basal seta. Free-living. Freshwater or brackish habitats. Type species: Tachidius (Neotachidius) triangularis Shen & Tai, 1963 = Neotachidius triangularis (Shen & Tai, 1963) comb. nov. [by monotypy] Other species: N. coreanus sp. nov.; N. parvus sp. nov., Published as part of Huys, Rony, Ohtsuka, Susumu, Conroy-Dalton, Sophie & Kikuchi, Yoshiaki, 2005, Description of two new species of Neotachidius Shen & Tai, 1963 (Copepoda, Harpacticoida, Tachidiidae) from Korean brackish waters and proposal of a new genus for Tachidius (Tachidius) vicinospinalis Shen & Tai, 1964, pp. 133-159 in Zoological Journal of the Linnean Society 143 (1) on pages 134-135, DOI: 10.1111/j.1096-3642.2004.00148.x, http://zenodo.org/record/5684683, {"references":["Shen C-J, Tai A-Y. 1963. On five new species, a new subgenus and a new genus of freshwater Copepoda (Harpacticoida) from the delta of the Pearl River, South China. Acta Zoologica Sinica 15: 417 - 432."]}

SINOTACHIDIUS GEN. NOV. Diagnosis: Tachidiidae. Condition of rostrum, integumental windows and mouthparts unconfirmed. Genital and first abdominal somites fused in ♀ original segmentation marked by transverse surface ridge dorsally and laterally; midventral copulatory pore positioned near posterior margin of genital double-somite (after Song & Chang (1995: fig. 1b)). Anal operculum spinulose. Caudal ramus setae IV – V well developed and pinnate. Sexual dimorphism in antennule, P2 endopod, P3 exopod (?), P5, P6 and urosomal segmentation. Antennule with numerous pinnate setae/spines; 7- segmented in both sexes; chirocer in ♂, with aesthetascs on segments 4, 6 and 7. Antenna with distinctly 2-segmented exopod; exp-1 with one seta, exp-2 with 0–1 lateral and two apical setae; lateral endopodal spine proximally displaced. Maxilliped with 1(?) accessory seta on endopod; claw minutely pinnate. P1–P4 enp-1 of normal size and with inner seta. Rami 3-segmented in P1–P4. P1 exp-3 with two outer spines, enp-3 with two inner setae. P3 enp-3 with five setae/spines. P4 enp-2 with one inner seta. Armature formula as follows: Exopod Endopod P1 0.1.122 1.1.221 P2 1.1.222 1.2.221 P3 1.1.222 1.2.221 P4 1.1.122 1.1.221 P 2 ♂ enp-2 with outwardly directed spinous apophysis; enp-3 small, anterior surface without transverse spinular comb, outer spine and outer distal seta rudimentary, inner setae well developed. P3 exopod ♂ presumably sexually dimorphic as in Neotachidius and Tachidius. P 5 ♀ slightly bilobate, separating outer lobe from endopodal lobe; outer lobe with basal seta and four exopodal elements (one seta, three spines); endopodal lobe with four pinnate spines. P 5 ♂ medially fused (?); each with four spines and two setae. P 6 ♀ represented by opercula closing off common genital slit, each with one seta. P 6 ♂ symmetrical; each member with two pinnate spines and naked outer basal seta. Free-living. Freshwater or brackish habitats. Type species: Tachidius (Tachidius) vicinospinalis Shen & Tai, 1964 = Sinotachidius vicinospinalis (Shen & Tai, 1964) comb. nov. Species inquirenda: Tachidius discipes Giesbrecht, 1881 sensu Song & Chang (1995). Etymology: The genus name is derived from the type genus Tachidius and the prefix sino, referring to the country of origin of the type species. According to Shen (1979) S. vicinospinalis has been recorded from brackish and freshwater habitats in both Guangdong and Fujian Provinces. Ovigerous females were encountered in April

NEOTACHIDIUS COREANUS SP. NOV. Type material: Holotype ♀ (NMNH reg. no. 251948) dissected and mounted on slides. Paratypes are 1 ♀ (NMNH reg. no. 251949) and 4 ♂♂ (NMNH reg. nos. 251950���53) dissected and mounted on slides; 20 ♀♀ and 20 ♂♂ in alcohol (NMNH reg. no. 251954); 11 ♀♀ and 5 ♂♂ in alcohol (NHM reg. nos. 2003.755���770). Type locality: Station 5 in a small river discharging into Kwangyang Bay, South Korea (34���57.1��N, 127���36.4��E), salinity 11.10��� (see Ohtsuka et al. 1992). Body length: ♀: 690 �� 40 mm (N = 53); ♂: 600 �� 40 mm (N = 51). Description Based on NMNH paratypes (reg. nos. 251949���53) and NHM paratypes (reg. nos. 2003.755���770). Female: Body robust (Fig. 1A), cyclopiform, with distinct separation between prosome and urosome. Rostrum (Figs 4B, 5A) weakly defined at base, ventrally directed, not discernible in dorsal aspect (Fig. 1A); elongate-ovoid with slightly constricted tip; dorsal surface with two pairs of sensillae and three median pores. Cephalosome (Figs 1A, 2A, 3A) with spinules along posterior margin and setules around lateroventral margins; with median dorsal and paired lateral integumental windows; sensillar and pore patterns as figured in Figure 1A. Tergite of first pedigerous somite rudimentary, represented by a transverse sclerite (Figs 1A, 2B; arrowed in Figs 2A, 3A, B) which is partly fused along its lateral sides to that of the second pedigerous somite. Somites bearing P2���P5 (Fig. 3A) with paired lateral integumental windows; free margins of tergites with long spinules all around except for denticulate dorsal margin of P4-bearing somite (Fig. 1A); dorsal surfaces with minute spinule rows, pores and sensillae as figured. P5-bearing somite with serrate posterior margin, with serrations being larger laterally than dorsally (Fig. 9C); lateral integumental windows largely concealed beneath tergite of preceding somite (Fig. 3A) and surrounded by spinule rows (Fig. 9C). Original segmentation of genital double-somite marked by bilateral constriction and dorsal serrate surface ridge. Genital field positioned ventrally on raised anterior half of double-somite (see lateral aspect; Fig. 9C). Genital apertures fused medially forming common genital slit (Figs 1B, 2C), closed off on either side by unisetose operculum derived from P6 (Figs 1B, 9C). Isolated copulatory pore not discernible, probably located medially within genital slit (Figs 1B, 2C). Single median seminal receptacle present (Fig. 9C). Raised ventral surface posterior to genital field with three spinule rows (anteriormost paired) (Figs 1B, 2C). Median integumental pore present anterior to genital slit (arrowed in Fig. 2C). Remaining urosomites with spinules around posterior margin and surface ornamentation as figured (Fig. 1A, B). Anal somite with two spinule rows dorsally and spinulose operculum (Fig. 10D). Caudal rami (Figs 1B, 10D) slightly convergent and slightly longer than wide, with oblique spinule row on dorsal surface and short row of fine spinules dorsolaterally (arrowed in Fig. 10D). With seven setae: I well developed, bare; II bare, displaced to near seta VII; III bipinnate and spiniform, with subapical flagellate extension; IV and V bipinnate and with fracture planes; VI swollen at base and typically with few spinules at inner proximal margin; VII bi-articulate at base and naked. Antennule (Fig. 4A) short, 7-segmented. Segment 1 with spinule rows around posterior and anterior margins. Armature formula: 1-[1 pinnate], 2-[1 naked +7 pinnate], 3-[5 naked +3 pinnate], 4-[3 pinnate + (1 naked + ae)], 5-[2 pinnate], 6-[2 naked +6 pinnate], 7- [5 naked +1 pinnate + acrothek]. Apical acrothek consisting of aesthetasc and plumose seta. Antenna (Fig. 4C, D) with spinule rows on abexopodal margin of basis and proximal endopod segment. Exopod incompletely 2-segmented; exp-1 shortest, with one pinnate spine; exp-2 with short pinnate spine fused to lateral margin and two unequal pinnate spines apically; few coarse spinules present around outer distal corner of exp-2. Distal endopod segment laterally with one naked spine in proximal third and one plumose seta plus one unipinnate spine in middle third (Fig. 4D); both lateral spines with subapical tubular extension. Apical armature of enp-2 consisting of one unipinnate spine and four geniculate setae; longest geniculate seta with long setules and fused at base to short pinnate seta; segment with various spinule rows as figured. Labrum (Fig. 5C) strongly developed, weakly trilobate; median lobe with short strong spinules along free margin and densely packed spinules plus a large median pore on posterior surface; lateral lobes each with double row of long spinules. Mandible (Fig. 3C, D). Gnathobase with series of blunt, multicusped teeth; dorsal corner with strong spine bearing minute spinules along dorsal margin and very coarse spinules along ventral margin. Basis relatively small, with two short plumose setae. Endopod longer than exopod, without surface spinules; with three plumose setae laterally (two fused at base) and nine setae apically (seven naked, two pinnate), several of which fused to segment. Exopod 1- segmented, with one short seta near proximal margin and four plumose setae along lateral margin and apex; distalmost three setae fused to segment. Paragnaths (Fig. 5C) strongly developed lobes with medially directed long spinules. Maxillule (Fig. 6B, C). Praecoxal arthrite with six spines, one pinnate seta and one minute tube-seta around distal margin; anterior surface with two juxtaposed setae; posterior surface with two pinnate setae, innermost very large and typically curved (Fig. 6C). Coxal endite with long spinules on anterior surface; with two smooth and three pinnate (of which one geniculate) setae. Basis with long setules on anterior surface; armature consisting of four naked and two pinnate (of which one geniculate) setae. Endopod a small segment with one plumose and two naked setae. Exopod represented by a single plumose seta. Maxilla (Fig. 9A). Syncoxa with three endites and long spinules along outer margin; proximal endite expanded distally, with one large and three shorter pinnate setae; middle and distal endites cylindrical, each with one naked and two pinnate setae. Allobasis with long setules along outer margin; drawn out into pinnate claw; accessory armature consisting of one naked and two pinnate setae. Endopod (Fig. 5B) indistinctly 2-segmented with one geniculate spine, two pinnate and three naked setae. Maxilliped (Figs 4E, 5E). Syncoxa with spinular row near medial distal corner and smaller spinules around proximal outer margin. Basis outer margin with slender spinules in proximal half. Endopod with curved claw and two minute accessory setae, one of which is tubular (Fig. 5E). P1 (Fig. 6A). Intercoxal sclerite bilobate, with strong spinules on anterior surface. Praecoxa well developed, with long spinules on anterior surface. Coxa with various anterior spinule rows as figured. Basis with produced lobate inner process bearing spinules anteriorly and setules posteriorly; outer and inner basal setae bipinnate. Rami 3-segmented. Exopod shorter than endopod; inner margin of segments with setules, outer margin with spinules; outer spines with subapical flagellate extension. Endopod with small enp-3; distal and outer margins of all segments with spinules; few spinules also present on proximal inner margin of enp-2 and -3; outer distal element of enp-3 spiniform and bipinnate. Posterior surface of endopod segments and exp-1 and -2 typically with spinule patches. P2-P4 (Figs 7A, 8A, 9B). Intercoxal sclerites with spinules anteriorly (P2���P4) and posteriorly (P2���P3). Praecoxa a small sclerite with anterior spinules. Coxa typically with very long spinules anteriorly and various spinule rows arranged around outer margin. Inner margin of basis forming lobate setulose expansion; with spinules around distal and outer margin as figured; outer basal seta bare (P2) or sparsely plumose (P3���P4). Endopods shorter than exopods; rami 3- segmented. Exp-1 and -2 (and - 3 in P4), and enp-2 and -3 typically with posterior spinule patches. Inner margin of exp-1 and -2 (and - 3 in P4) with few long setules; spinular ornamentation around distal and outer segment margins as figured. Exp-3 of P2���P3 forming spinous extension between bases of distal outer spine and outer apical spine. Armature formula of P1���P4 as for genus. P5 (Fig. 7D) about 1.05 times as long as maximum width; typically with distinct outer concavity, separating outer lobe from distal portion; with numerous spinular rows on both posterior and anterior surfaces as figured; outer lobe with basal plumose seta and pinnate spine; distal portion with plumose seta flanked by strong pinnate spines around apex, and two pinnate spines along inner margin; anterior surface with three secretory pores (one marginal). Male: Sexually dimorphic in size, urosome ornamentation and segmentation, antennule, P2 endopod, P3 exopod, P5 and P6. Antennule (Fig. 10B) 7-segmented, with one segment distal to geniculation (chirocer condition). Segment 1 with sclerite around base; posterior margin forming lobate extension bearing long spinules; with numerous spinule rows around anterior margin as figured (Fig. 10B, C). Segment 3 with bulbous process on proximal posterior margin bearing plumose seta. Segment 4 largely membranous around posterior margin; anterior margin with dorsal spinous process. Segment 5 minute, represented by a small sclerite on anterior margin (Fig. 14D; arrowed in Fig. 15B for N. parvus). Segment 6 (Fig. 14D) very large and swollen; with incomplete transverse surface suture ventrally and posteriorly; anterior margin forming multicuspidate structure (typically with eight cusps) in proximal half; with modified longitudinally striated element often closely adpressed to anterior surface (Fig. 14D; cf. Fig. 15D for N. parvus). Segment 7 (Figs 10B, 14E) hook-shaped, without surface sutures marking original segmentation; apex weakly chitinized, recurved; anterior surface forming longitudinal furrow containing two basally fused elements (arrowed in Fig. 14C) as in N. parvus (Fig. 15C). Armature formula: 1-[1 pinnate], 2-[1 pinnate], 3-[6 bare +5 pinnate], 4-[6 bare +2 pinnate + ae], 5-[2 pinnate], 6-[9 bare +3 pinnate +1 striated element + (1 + ae)], 7-[12 +2 modified + acrothek]. Apical acrothek consisting of short aesthetasc and small naked seta. Many setae on segments 3���4 with proximal flexure zone. P2 endopod (Figs 7B, 16A, C). Middle segment enlarged on inner margin, forming outwardly directed spinous apophysis partly overlying enp-3 anteriorly; inner setae markedly shorter than in ♀. Enp-3 small (Figs 7C, 16A), with row of long setules on anterior surface, typically overlying apex of spinous apophysis; outer distal seta strongly reduced, represented by minute, basally fused spine with recurved tip; outer spine reduced. P3 exopod (Fig. 8B) distinctly longer and more slender than in ♀. Inner setae of exp-1 and -2 smaller than in ♀. Exp-2 elongate; posterior spinules absent. Exp-3 longer than in ♀ inner distal seta vestigial. P5 (Figs 6D, 10A) medially fused, each with three pinnate spines and two setae; outermost seta naked, representing outer basal seta, other seta sparsely plumose. Anterior surface with fine spinule rows and pore. P6 (Figs 6D, 10A) symmetrical; each member with two pinnate spines and naked outer basal seta; posterior margin with coarse spinules bi-laterally and fine spinules medially. Spermatophore large, about 100 mm in length. Ornamentation of urosome essentially as in ♀ except for more elaborate spinular patterns on first abdominal somite (Figs 6D, 10A). Etymology: The specific name refers to Korea, the country where the type locality of the new species is situated., Published as part of Huys, Rony, Ohtsuka, Susumu, Conroy-Dalton, Sophie & Kikuchi, Yoshiaki, 2005, Description of two new species of Neotachidius Shen & Tai, 1963 (Copepoda, Harpacticoida, Tachidiidae) from Korean brackish waters and proposal of a new genus for Tachidius (Tachidius) vicinospinalis Shen & Tai, 1964, pp. 133-159 in Zoological Journal of the Linnean Society 143 (1) on pages 135-147, DOI: 10.1111/j.1096-3642.2004.00148.x, http://zenodo.org/record/5684683, {"references":["Ohtsuka S, Yoon YH, Endo Y. 1992. Taxonomic studies on brackish copepods in Korean waters. I. Redescription of Tortanus dextrilobatus Chen & Zhang, 1965 from Korean waters, with remarks on zoogeography of the subgenus Eutortanus. Journal of the Oceanological Society of Korea 27: 112 - 122."]}

Two new sympatric species of Neotachidius Shen & Tai, 1963, N. coreanus sp. nov. and N. parvus sp. nov., are described from plankton samples collected from brackish waters in Kwangyang Bay, South Korea. Morphological differences with the type species N. triangularis (Shen & Tai, 1963) comb. nov. are discussed in detail. Korean material from Chindo Island, previously identified as N. triangularis by Song and Chang in 1995 is at least partly based on N. parvus sp. nov. The occurrence of N. triangularis in estuaries in British Columbia and Washington is attributed to transoceanic transport by ballast water from cargo ships entering the Columbia River or neighbouring estuaries. The subgeneric division of the genus Tachidius proposed by Shen and Tai in 1963 is rejected and instead full generic rank is assigned to both Tachidius and Neotachidius. The taxonomic position and original description of Tachidius (Tachidius) vicinospinalis Shen & Tai, 1964 are reviewed and the species is designated as the type species of a new genus Sinotachidius gen. nov. The latter and Neotachidius form a clade which stands in apposition to Tachidius. Tachidius discipes Giesbrecht, 1881 sensu Song & Chang is considered species inquirenda in Sinotachidius gen. nov. © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society, 2005, 143, 133–159.

NEOTACHIDIUS PARVUS SP. NOV. Synonym: Tachidius (Neotachidius) triangularis Shen & Tai, 1963 sensu Song & Chang (1995) [partim]. Type material: Holotype ♀ (NMNH reg. no. 251942) dissected and mounted on slides. Paratypes deposited in NMNH are 2 ♀♀ (reg. no. 251943���944) and 3 ♂ (reg. nos. 251945���947) dissected and mounted on slides; 20 ♀♀ and 20 ♂♂ in alcohol (reg. no. 251973). Paratypes deposited in NHM are 1 ♀ dissected on ten slides (reg. no. 2003.808), 1 ♂ dissected on seven slides (reg. no. 2003.809); 24 ♀♀ and 13 ♂♂ in alcohol (reg nos. 2003.771���807) Type locality: Stn five in a small river discharging into Kwangyang Bay, South Korea (34���57.1��N, 127���36.4��E), salinity 11.10��� (see Ohtsuka et al., 1992). Additional material: (1) Taehwa River estuary, Ulsan, South Korea; leg. C.Y. Chang, 31 January 1987; 1 ♀ and 1 ♂ in alcohol (NHM reg. nos. 2003.812���813). (2) Jochean, Cheju Island, South Korea; leg. C.Y. Chang and S. J. Song, 27 October 1993; 2 ♀♀ in alcohol (NHM reg. nos. 2003.810���811). Body length: ♀: 500 �� 30 mm (N = 53); ♂: 450 �� 30 mm (N = 53; based on paratypes). Neotachidius parvus is closely related to N. coreanus and the description below is consequently restricted to differences only. Description Based on NHM paratypes (reg. nos. 2003.771���809). Female: Spinules around posterior margin of cephalosome and somites bearing P2���P3 shorter than in N. coreanus (Fig. 11A). Slight differences in fine surface spinulation of pedigerous somites as illustrated in Figure 11A. Rudimentary tergite of P1-bearing somite less well defined. Posterior margin of P4-bearing somite denticulate laterodorsally but smooth dorsally; dorsolateral spinules shorter than in N. coreanus. P5- bearing somite with spinules around lateroventral corner of pleurotergite; lateral surface spinules distinctly shorter and more blunt than in N. coreanus (Fig. 11C). Dorsal posterior margins of genital double-somite and free abdominal somites 2���3 denticulate instead of with long spinules (Fig. 11A, C); spinules along ventral posterior margin of these somites shorter than in N. coreanus (Fig. 11B). Paired spinule rows posterior to genital slit absent (compare with N. coreanus: Figs 1B, 2C); remaining two rows consisting of smaller spinules (Fig. 11B, C). Genital field area less raised in lateral aspect (Fig. 11C). Lateral surface ornamentation of genital double-somite less elaborate than in N. coreanus (Fig. 11C). Anal somite with paired laterodorsal spinule rows but without spinules dorsally (Fig. 13D). Anal operculum spinulose but spinules markedly shorter than in N. coreanus. Caudal rami (Figs 11B, 13D) slightly longer than wide but shorter than in N. coreanus; armature and ornamentation essentially as in N. coreanus, except dorsolateral spinule row (arrowed in Fig. 10D) absent. Antennule (Fig. 12A) with short apical segment, only slightly longer than segment 6. Armature as in N. coreanus. Antenna (Fig. 12B) with spinule rows on abexopodal margin of basis and proximal endopod segment. Exopod distinctly 2-segmented; exp-1 shortest, with one long slender plumose seta; exp-2 with short smooth seta fused to lateral margin and two unequal plumose setae apically; spinular ornamentation around outer distal corner of exp-2 more elaborate than in N. coreanus. Distal endopod segment laterally with one unipinnate spine in proximal third and one smooth seta plus one unipinnate spine in middle third. Apical armature of enp-2 consisting of one unipinnate spine and four geniculate setae; longest geniculate seta with few spinules and fused at base to short naked seta; segment with various spinule rows and surface frills as figured. Mandible. Palp with similar armature as in N. coreanus. Endopod with spinule row on anterior surface (arrowed in Fig. 5D). Maxillule, maxilla and maxilliped as in N. coreanus. P1 (Fig. 12C). Most spinules on anterior surface of praecoxa and coxa and around distal margin of basis distinctly shorter than in N. coreanus. Inner basal seta more slender and longer, reaching beyond distal margin of enp-2. Rami as in N. coreanus except for inner distal element of enp-3 (arrowed in Fig. 12C) being long, plumose and setiform instead of pinnate and spiniform. P2���P4 (Figs 12D, 13A) as in N. coreanus except for (a) intercoxal sclerites with spinules anteriorly but not posteriorly; (b) long spinules on anterior surface of coxa absent; (c) spinules around distal margin of basis uniform in size; (d) posterior spinules on P4 coxa absent, and (e) P4 exp-3 with only one spinule row on posterior surface. P5 (Fig. 13C) longer and with outer concavity less pronounced than in N. coreanus; about 1.40 times as long as maximum width; spinule pattern on anterior surface and along inner margin different (as illustrated in Fig. 13C); apical seta smooth instead of plumose; spines more slender than in N. coreanus. Male. Sexually dimorphic in size, urosome ornamentation, antennule, P2 endopod, P3 exopod, P5 and P6. Antennule (Figs 14A, 15A���D) as in N. coreanus except for two differences on segment 6: (a) multicuspidate process (Figs 14A, 15B; b in Fig. 15D) less pronounced and typically with five cusps, and (b) cylindrical process adjacent to longitudinally ribbed element (a in Fig. 15D) with two spinulose elements (ventralmost smooth in N. coreanus; arrowed in Fig. 14D). Armature formula: 1-[1 pinnate], 2-[1 pinnate], 3-[6 bare +5 pinnate], 4-[6 bare +2 pinnate + ae], 5-[2 pinnate], 6-[8 bare +4 pinnate +1 striated element + (1 + ae)], 7-[12 +2 modified + acrothek]. P2 endopod (Figs 13B, 16B). Enp-1 comparatively longer than in N. coreanus with outer distal corner not spinous; spinules along outer margin longer, those of inner distal corner shorter than in N. coreanus. Middle segment transversally enlarged but markedly shorter than in N. coreanus; outer margin distinctly convex; both inner setae markedly shorter than in N. coreanus. Enp-3 small (Fig. 16B), with row of long setules on anterior surface covering spinous apophysis of enp-2; outer distal seta strongly reduced, represented by a short and blunt, basally fused element (arrowed in Fig. 13B). P3 exopod (Fig. 12E) more robust than in N. coreanus, with exp-2 being distinctly shorter; inner setae of exp-3 shorter. P3 endopod about as long as in N. coreanus but enp-3 proportionally longer. P5 (Fig. 14B, C) medially fused with medial incision more pronounced than in N. coreanus; each with three serrate spines and two naked setae; middle and inner spines shorter than in N. coreanus; anterior surface spinules absent; spinules around midventral distal margin coarser than in N. coreanus. P6 (Fig. 14B, C) symmetrical; each member with two serrate spines and naked outer basal seta; spinules around medial distal margin uniform in size and coarser than in N. coreanus. Ornamentation of urosome essentially as in N. coreanus except for size of spinules (Fig. 14B, C). Variability: The females from Cheju Island were larger in size (575���579 mm). Etymology: The specific name is derived from the Latin parvus, meaning small, and alludes to the small size of the present species., Published as part of Huys, Rony, Ohtsuka, Susumu, Conroy-Dalton, Sophie & Kikuchi, Yoshiaki, 2005, Description of two new species of Neotachidius Shen & Tai, 1963 (Copepoda, Harpacticoida, Tachidiidae) from Korean brackish waters and proposal of a new genus for Tachidius (Tachidius) vicinospinalis Shen & Tai, 1964, pp. 133-159 in Zoological Journal of the Linnean Society 143 (1) on pages 147-150, DOI: 10.1111/j.1096-3642.2004.00148.x, http://zenodo.org/record/5684683, {"references":["Shen C-J, Tai A-Y. 1963. On five new species, a new subgenus and a new genus of freshwater Copepoda (Harpacticoida) from the delta of the Pearl River, South China. Acta Zoologica Sinica 15: 417 - 432.","Song SJ, Chang CY. 1995. Marine harpacticoid copepods of Chindo Island. Korean Journal of Systematic Zoology 11: 65 - 77.","Ohtsuka S, Yoon YH, Endo Y. 1992. Taxonomic studies on brackish copepods in Korean waters. I. Redescription of Tortanus dextrilobatus Chen & Zhang, 1965 from Korean waters, with remarks on zoogeography of the subgenus Eutortanus. Journal of the Oceanological Society of Korea 27: 112 - 122."]}

The harpacticoid copepod subfamily Thompsonulinae Lang, 1944, formerly recognized as belonging to the family Tachidiidae (Lang, 1948) is raised to family rank and redefined to include only the genera Thompsonula T. Scott and Caribbula gen. nov. Thompsonula hyaenae (I. C. Thompson) and T. curticauda (Wilson) are redescribed and refigured. Re-examination of the original material showed that Wilson's Rathbunula agilis is synonymous with T. curticauda and not with T. hyaenae, as suggested by Lang (1948). It is now clear that the two species of Thompsonula have distinct distributions, T. curticauda being confined to the North American continent and T. hyaenae to western Europe and the Mediterranean. The genus Caribbula is established to accommodate the type species, T. hyaenae elongata (Gee) and C. fleegeri sp. nov. which are described and figured. The genus Caribbula is distinguished from Thompsonua, primarily by the unique sexual dimorphism on the exopod of P4 and, at present, is known only from the eastern seaboard of the United States and Gulf of Mexico. The genera Danielssenia, Psammis, Paradanielssenia, Micropsammis and Leptotachidia are tentatively assigned to the family Paranannopidae Por.

From an examination of the original material of G. O. Sars and new material from Bjornehodebukta, Oslofjord, Psammis longisetosa Sars is redescribed, noting in particular the presence of 2 inner setae on P2 endopod 2 and 1 inner seta on P4 exopod 1. A new species is described from the Celtic Sea, Paradanielssenia biclavata, characterized by the presence of club-shaped appendages on the mouthparts and differing from P. kunzi Soyer in mouthpart structure and limb setation. Specimens from the Gulf of Mexico have been assigned to a new subspecies, Thompsonula hyaenae elongata, after careful comparison with specimens of the nominate T. hyaenae (I. C. Thompson) from Europe and South Carolina.