Nicidion Kinberg, 1865, and Paramarphysa Ehlers, 1887, were previously recognized as abranchiate groups of Eunice Cuvier, 1817, and Marphysa de Quatrefages, 1865, respectively. However, recent studies have demonstrated Nicidion is monophyletic, and the genus was redefined. Likewise, the character presence/absence of peristomial cirri, which traditionally was used to differentiate between Nicidion and Paramarphysa, is now considered non-diagnostic. Subsequently, the type species of Paramarphysa was recently transferred to Nicidion, implying that they are synonyms. Despite the above, some abranchiate species are still classified in Marphysa, raising the question of their positions within the genus. In the present study, we re-examined seven abranchiate species, studying their type material, and reviewing the literature, intending to disclose their taxonomic status. We concluded that only four of them belong to Nicidion: N. parvipes (Benham, 1927) n. comb., N. posteriobranchia (Day, 1962) n. comb., N. proppi (Averincev, 1972) n. comb., and N. saxicolas (Langerhans, 1881) n. comb. Two species, Marphysa simplex Langerhans, 1884, and Marphysa orientalis (Willey, 1905), were considered indeterminable. And one, ?Palola teres (Treadwell, 1922), is now considered incertae sedis because of insufficient information available. Additionally, we provided redescriptions of N. cincta Kinberg, 1865, type species of Nicidion, and N. hentscheli (Augener, 1931). Further character analysis on all Nicidion species suggested the genus consists of two groups (G1, G2) based on the distribution and presence and form of branchiae, the architecture of maxilla II, and the shape of the body’s posterior region. Also, the study of these and other characters such as the distribution of the swollen base of the ventral cirri and the coloration of the aciculae throughout the body, allow us to redefine the diagnosis of Nicidion.

Nicidion Kinberg（1865年）和Paramarphysa Ehlers（1887年）以前分别被公认为分别是1817年的Eunice Cuvier和1865年的Marphysa de Quatrefages的花生酸酯类。但是，最近的研究表明，杀ic虫是单系的，并且该属已被重新定义。同样，传统上用来区分Nicidion和Paramarphysa的是否存在蠕虫性字符，现在被认为是非诊断性的。随后，模式种Paramarphysa最近已转让给Nicidion，表示它们是同义词。尽管如此，一些abranchiate品种仍归入Marphysa，提高属中的位置的问题。在本研究中，我们重新检查了7种阿魏酸属物种，研究了它们的类型材料，并复习了文献，以期揭示其分类学地位。我们得出的结论是，其中只有四个属于Nicidion：N。帕尔维佩斯（Benham，1927）梳，Ñ。后支气管（Day，1962）梳，Ñ。proppi（Averincev，1972）。梳子。，和Ñ。saxicolas（Langerhans，1881年）梳子。两种单纯的玛格莎（Marphysa）朗格罕（Langerhans）（1884）和东方玛格莎（Marphysa Orientalis）（Willey，1905）被认为是不确定的。和一，？Palola小圆（崔德威尔，1922），目前被认为是地位未定，因为资料不足。此外，我们提供了N的重新描述。cincta Kinberg，1865年，Nicidion和N的类型种。亨切利（1931年，奥格纳）。所有Nicidion的进一步字符分析根据物种的分布和存在，形态，上颌II的结构以及身体后部区域的形状，该属可分为两类（G1，G2）。此外，对这些及其他特征（例如腹侧腹底肿胀的分布以及整个体内的球菌的着色）的研究，使我们能够重新定义杀ic虫的诊断。