Type fixation for each of the 601 valid genera ( 17 placed incertae sedis) and 13 genera of doubtful identity ( genera inquirenda) in the Harpacticoida ( Crustacea, Copepoda) has been verified. Twenty-four genus-group names published after 1930 lack the mandatory type fixation and are therefore unavailable. With the exception of Kliopsyllus Kunz, 1962 which is replaced by its senior synonym Emertonia Wilson, 1932, such names are made available here by either attributing the original name to the first author(s) who explicitly fixed a type species (Psammastacus Nicholls, 1935; Alteuthellopsis Lang, 1944; Idyellopsis Lang, 1944; Paralaophonte Lang, 1944; Robertgurneya Lang, 1944; Cladorostrata Shen & Tai, 1963; Micropsammis Mielke, 1975; and the subgenera Rheocamptus Borutzky, 1948 and Scottopsyllus Kunz, 1962;) or by adopting the name taking the present authorship and date (Paranannopus Lang, 1936a; Paraidya Sewell, 1940; Apodopsyllus Kunz, 1962; Scottolana Por, 1967; Barbaracletodes Becker, 1979; Ameiropsyllus Bodin, 1979; Chilaophonte Mielke, 1985; Psammonitocrella Rouch, 1992; Tectacingulum Harris, 1994; and the subgenera Intermedopsyllus Kunz, 1962 ( corrected spelling Intermediopsyllus) and Fiersiella Suarez Morales & Iliffe, 2005). In two cases a ruling by the International Commission on Zoological Nomenclature will be required to avoid upsetting a long-accepted name in its accustomed meaning (Halectinosoma Lang, 1944; Heterolaophonte Lang, 1944). The recently proposed generic name Pilocamptus Wells, 2007 does not satisfy the provisions of ICZN Art. 13.1 and is here made available by explicit citation of a bibliographic reference that provides a diagnosis purported to differentiate the taxon. Rhizothrix Brady & Robertson, 1876 is an unavailable name which was first made available by Sars (1909a). The unavailable generic name Scottopsyllus Kunz, 1962 has no potentially valid synonym and is replaced by the next oldest available name from among its subgenera, i.e. Wellsopsyllus Kunz, 1981 (ICZN Art. 23.3.5). The unavailable subgeneric name Psyllocamptus (Langpsyllocamptus) Kunz, 1975b is not reinstated because it denotes a taxon that is based exclusively on plesiomorphies. New replacement names have been proposed for preoccupied generic names in the harpacticoid families Canthocamptidae (Poria Lang, 1965; Dahlakia Por, 1986a), Dactylopusiidae (Sewellia Lang, 1965), and Leptopontiidae (Ichnusella Cottarelli, 1971). The preoccupied generic name Anoplosoma Sars, 1911c (family Ameiridae) is replaced by a previously proposed, but subsequently forgotten, replacement name, Anoplosomella Strand, 1929. Nomina nova are also suggested for Parathalassius Dussart, 1986 (Calanoida: Centropagidae) and Berea Yamaguti, 1963 (Cyclopoida: Chondracanthidae) which have entered into homonymy with previously established names. The junior synonym Alteutha Baird, 1846b is considered valid, taking precedence as a nomen protectum over the older names Sterope Goodsir, 1845 and Carillus Goodsir, 1845 (nomina oblita). Similar reversal of precedence applies to the family-group names Peltidiidae Claus, 1860 and Tisbidae Stebbing, 1910 which are junior subjective synonyms of Steropinae Dana, 1854 and Scutellidiinae Claus, 1889, respectively. Since the type of Idomene Philippi, 1843 is identified as a member of the Clausidiidae ( Cyclopoida), the generic name Xouthous Thomson, 1883 is reinstated to accommodate all remaining species currently placed in Idomene. The forgotten copepod genus Microchelonia Brady, 1918 is placed in the family Laophontidae and considered a senior subjective synonym of Namakosiramia Ho & Perkins, 1977. The family-group name Pontostratiotidae A. Scott, 1909 ( type: Pontostratiotes Brady, 1883) is a senior subjective synonym of Cerviniopseinae Brotskaya, 1963 (type: Cerviniopsis Sars, 1903) and the former is consequently reinstated at the subfamilial level. The family-group name Huntemanniidae Por, 1986a (type: Huntemannia Poppe, 1884) is a junior subjective synonym of Nannopinae Brady, 1880a (type: Nannopus Brady, 1880a) and the latter is reinstated as the valid name at family rank and with the spelling corrected to Nannopodidae. The family-name Paranannopinae Por, 1986a is a nomen nudum based on an unavailable generic name and is replaced by Danielsseniinae Huys & Gee in Huys et al., 1996. Four orphaned taxonomic groupings created by the removal of the type species - but not of the remaining species included in a genus - require an existing ( previously invalid) or new generic name. Amphiascus Sars, 1905a is a senior objective synonym of Paramphiascopsis Lang, 1944 and must be restricted to the species currently included in the latter; a new genus Sarsamphiascus (type: Dactylopus minutus Claus, 1863) is proposed to receive all remaining Amphiascus species. The new generic names Monardius gen. nov. and Glabrotelson gen. nov. are proposed for the orphaned taxonomic groupings resulting from the removal of the types of Teissierella Monard, 1935a to Robertsonia Brady, 1880a, and of Hastigerella Nicholls, 1935 to Arenosetella Wilson, 1932, respectively. Leptomesochra Sars, 1911b is a senior subjective synonym of Interleptomesochra Lang, 1965 and must be restricted to the latter's taxonomic concept; the previously unavailable generic name Leptameira Lang, 1936d is reinstated under the present authorship and date to assemble all remaining Leptomesochra species. Type species are fixed for a number of genera that were proposed before 1931 without original type designation: Marshia Herrick, 1895; Cerviniopsis Sars, 1903; Pseudobradya Sars, 1904a; Alteuthella A. Scott, 1909; Diosaccopsis Brian, 1925a; and Nannopodella Monard, 1928. Xouthous sarsi sp. nov. is proposed for Idomene forficata Philippi, 1843 sensu Sars (1906a). Tachidius longicornis Olofsson, 1917 is reinstated and placed in the genus Geeopsis Huys in Huys et al., 1996 as G. longicornis ( Olofsson, 1917) comb. nov. Micropsammis galapagoensis Mielke, 1997 is transferred to Telopsammis as T. galapagoensis ( Mielke, 1997) comb. nov.