Yellow in color. Body strongly narrowed caudad. Prostomium short and broad. The palpal lobes large and rounded, bulging conspicuously forward and ventrad; separated by a deep furrow. Tentacles in a slightly curved transverse line, the outer paired tentacle on each side lying a little farther forward than the inner. Ceratophores very short and not broader than bases of styles, exceeded by the first segment of style which about equals the next two in length. The styles in general strongly moniliform, the articles short and well rounded. The styles in types short but not in any case certainly complete; the number of articles present from nine to twelve. The peristomium much longer than the prostomium than which it is also clearly wider and higher; entire second somite very short, not more than one-fourth as long as I. Nuchal cirri short and conical, much shorter than the peristomium, transversely wrinkled or sometimes distinctly annulated. Notocirri slenderly conical, becoming more slender in posterior region as usual; with some weak encircling wrinkles but not distinctly divided into articles. Branchiæ begin as single filaments on IX or sometimes on VIII. Branchiæ of X each consisting of two filaments. The number in several of the succeeding branchiæ increases to three, then again falling to two, and, finally, the last eight pairs or so are again simple filaments. The last branchiæ in the type occur on XXXII. Anal cirri short, slenderly conical. Maxillae strongly chitinized; brown, with edges in part black. In maxillae II the right plate has six large teeth, the outer left plate four and the odd or inner left plate seven or eight. III with nine teeth or crenulatious. Number of segments in type one hundred and nine. Length, 43 mm.; greatest width, exclusive of parapodia, 2.6 mm. An incomplete larger specimen has a width of 3.2 mm. Type--M. C. Z. 2, 154. Taken among holdfasts of kelp. (C. F. Baker, June 30, 1911.) _Arabella lagunae_ sp. nov.