Recent records of the occurrence of a little-known ribbon worm, Nipponnemertes ogumai (Yamaoka 1947), along the Pacific coast of Honshu, Japan, are summarized with a map of known distribution. Photographs of the worm in its living state are provided, with brief descriptions of external morphology and behavior. Sequences of the nuclear 18S rDNA (1,785 bp) and 28S rDNA (2,215 bp), as well as the mitochondrial 16S rDNA (452 bp) and cytochrome c oxidase subunit I (COI) gene (621 bp) were determined. Preliminary maximum-likelihood phylogenetic analyses were performed together with some other congeners, viz., N. bimaculata (Coe 1901), N. pulchra (Johnston 1837), N. punctatula (Coe 1905), and two unidentified forms, for which sequences were available in the public databases. In the resulting tree, N. ogumai was nested within the congeners, consolidating the previous alteration of the generic placement of the species from Amphiporus Ehrenberg (1828-1831), to Nipponnemertes Friedrich 1968. A contaminated cytochrome c oxidase subunit I (COI) sequence implied that N. ogumai may feed on caridean shrimps.
