WILLEMSIA GEN-NOV AND BOREOPONTIA WILLEMS, 1981 REVISITED (HARPACTICOIDA, CYLINDROPSYLLIDAE)

A new genus and species of Cylindropsyllidae (Copepoda, Harpacticoida) , collected from shallow subtidal sand in the Southern Bight of the No rth Sea, is described and illustrated. Willemsia calceola gen. et sp. n. exhibits a unique kind of sexual dimorphism on the male P3 not obse rved thus far in any other harpacticoid. It is further distinguished f rom all known Cylindropsyllinae by the absence of an isolated midventr al copulatory pore, the facies of the P2-P3 in the female and the pecu liar shape and orientation of the fifth pair of legs in both sexes. Ba sed on the sexual dimorphism of the P2 exopod and P3 endopod, it is su ggested that W. calceola shares a sistergroup relationship with Stenoc aris kerguelenensis BODIOU, 1977 which is transferred to a new genus N avalonia. Boreopontia heipi WILLEMS, 1981 is redescribed and an update of its distribution in the North Sea is given. Stenocaris pygmaea NOO DT, 1955, previously ranked as a junior subjective synonmy of S. ponti ca CHAPPUIS & SERBAN, 1953, is reinstated. The homology of spinous pro cesses on the caudal rami in species of Boreopontia WILLEMS, Stenocari s SARs and Stenocaropsis APOSTOLOV is assessed.