Somewhat resembling _P. elongata_ (Johnson), which also occurs in this region, but differing in having the dorsum pigmented throughout, being black or slaty with pale lines between the segments and dividing each of the latter transversely excepting across the middorsal region. The pigmentation may sometimes be very dilute. In technical details readily distinguished from that species, e. g., in the different form of the appendage of the setae, this being obviously more elongate and erect and proportionately more slender. Two or more dorsal setae differ in having shorter, more strongly curved appendages which are wholly smooth on the concave edge instead of being pubinate to beyond middle as in the others. Prostomium rather short and broad. Palpi thick the ectal lobe small as compared with the principal or mesal one; united only at base. Eyes small, transversely elongate and often curved, the two on each side close together and sometimes almost fused, with the posterior one well mesad of but only a little caudad of the anterior one. Median tentacle situated midway between the two eye groups in a longitudinal furrow dividing prostomium; composed of eighteen to twenty-three short articles. Each paired tentacle at corner of prostomium in front of eye-group of corresponding side; similar in form and size to the median tentacle. Lower tentacular cirrus about equalling a tentacle in length, the dorsal longer, both of similar form. First segment extending forward in a rounded or subtriangular lobe or flap at middle above. The notocirri attached above bases of parapodia as usual; long, composed of numerous short segments; much longer than the tentacles, each average one when laid back along body ordinarily passing over three or three and a half segments. Neurocirri short, stout, fusiform. Body slender, narrowed moderately at the ends, elsewhere of nearly uniform width. Type composed of seventy-three segments. Length, near 20 mm. Type--M. C. Z. 2, 148. Littoral zone. _Pionosyllis lucida_ sp. nov.