Length of incomplete specimen not in excess of 12 mm.; greatest width, .8 mm.
This form seems to be close to _P. alata_ Moore. The type, which is much smaller than that of _alata_, differs in various details from the description of the latter. The principal lateral wings are confined to the third segment and are united across the dorsum of third somite instead of involving the anterior border of IV and crossing the latter above; connecting dorsal fold low and lacking any forwardly directed process; the wing rises as a high, rounded lobe on each side just below level of setigerous tubercles, rising high above the middorsal surface. In addition to the prominent wings on III there is on IV on each side a much lower ridge or wing paralleling that on III, this not more prominent above. Unlike those of _alata_, somites II and III are not confounded laterally but are distinct throughout. Prostomium short. Tentacles mostly lost in type; rather slender, not long, apparently in but a single transverse series. Peristomium deeply excavated at middle below, the bottom of the excavation rounded and the peristomium produced on each side of this into the usual large lobes. The branchiæ, as in the genotype and other species, strongly asymmetrically developed. The right anterior branchia is much the largest, the trunk very long, with the left anterior much smaller. Of the posterior pair, the right, unlike that of _alata_, is also much larger than the left one. In the type the sternal plates are not sharply differentiated. The manubriate uncini of V have the general form of those in _alata_, but the bulge below the beak is much larger and more rounded with the subrostral tooth more obtuse and nearer the middle of the oblique edge; beak less divergent from manubrium; vertex with three transverse series of denticles. The color in the abdominal region light fulvous, in the thoracic darker with a narrow brownish stripe along caudal border of each segment laterally and ventrally. Type not quite complete caudally, retaining eighty somites.
The wall of the tube is composed of sand and shell fragments.
Prostomium short; with numerous tentacular filaments. Uncini avicular and of same form throughout. Setæ beginning on third somite; tips simple. Uncini beginning on the fourth somite. No lateral foliaceous lobes on the anterior segments. Branchiæ two pairs; branched; attached on somites II and III.