One new species of Stegocephalus Krøyer, 1842 (Amphipoda, Stegocephalidae) described from a seamount of the Caroline Plate, NW Pacific.

A new species of the subfamily Stegocephalinae, Stegocephaluscarolus sp. nov. , is described from a seamount in the Caroline Plate. Two related species, S.cascadiensis (Moore, 1992) and S.longicornis (Gurjanova, 1962), were previously reported in the North Pacific. Important morphological characters which differentiate S.carolus sp. nov. from S.cascadiensis are found in antenna 1, the mouthparts, pereopod 7 and the length of rami of uropods 2 and 3. The new species differs from S.longicornis by characters of antenna 1, the mouthparts and the shape of epimeral plate 3. Additionally, the morphological differences between the new species and the remaining seven species of Stegocephalus are also presented.