A new genus and species, Janstockia phallusiella n. gen., n. sp., of the family Notodelphyidae is described from Phallusia nigra Savigny, 1816 collected in the Suez Canal. The new genus is most closely related to Ophioseides Hesse, 1864. Supplementary morphological observations are presented on the type species of the latter genus, Ophioseides cardiocephalus Hesse, 1864, and the two genera are compared. The genera differ especially in the form of the maxillules, which have a complex trilobate structure in Janstockia n. gen., and the maxillipeds, which are two-segmented in Janstockia n. gen. The structure of the swimming legs in these two genera is re-interpreted.
Crustacea, Copepoda, Cyclopoida, Janstockia n. gen., parasite d’ascidies, Canal de Suez, nouveau genre, nouvelle espèce.