Length of type, exclusive of branchiæ, 40 mm.; greatest width, 6.2 mm.
The body in general light brown; but ventrally there is a median longitudinal fulvous stripe over the ventral plates. The branchiæ are crossed by a series of dark bands or annuli which fade out proximally, about three distad of the middle of length being deep and distinct. There are nineteen pairs of branchial radioles; barbs numerous, densely arranged to near tip, the naked distal region of axis very short, pale excepting where partially or completely involved by the transverse dark bands. Ventral lobes of collar moderate, rounded, edges a little rolled down; dorsal ends separated; no lateral incisions, being but two-lobed; not produced forward below, lobes rounded and separated. Thoracic segments eight. Ventral plates all rectangular, those of the abdomen divided by the midventral sulcus. Total number of segments, sixty.
Length without branchiæ, 21 mm.; length with branchiæ, 28 mm.; greatest width, 3 mm.
The general color is dusky or pale brownish with the anterior ventral plates lighter and the branchiæ rather weakly transversely banded with dark. Radioles of branchiæ in a simple series; seventeen pairs. Collar well developed, produced forward below in two pointed lobes overlapping at the middle. Eight setigerous thoracic somites. Most dorsal thoracic setæ in each fascicle long and finely pointed with wings narrow; the ventral setæ much more numerous, shorter, spatulate, with fine tip. The uncini have the posterior process very short, rounded at the end, much shorter and more slender than the neck, which is rather strongly curved; vertex high and narrowly rounded; beak not strongly depressed. Type incomplete, only seven of the abdominal segments being present.
Length of first sixteen segments, 15 mm.; including branchiæ, 21 mm.; width, 2.5 mm.
The type is notably marked with black pigment; the collar membrane crossed with a close series of longitudinal dark stripes, one in line with each radiole and narrowing caudad; the branchiæ crossed transversely with dark bands. Thoracic somites, more notably the anterior ones, with a dusky to black band in front of each uncinigerous torus and a dark spot on the dorsum mesad of the setigerous papilla. The collar with a dark area ventrad and also dorsad of the fascicle. Ground color greyish of light brown cast, lacking the yellow dominating in omissa. Sixteen (or seventeen) pairs of radioles in the branchiæ. Ventral lobes of collar pointed, widely overlapping in the median line, dorsal ends free, projecting toward each other in dorsal groove. Setigerous thoracic somites eight in number. Inferior setæ numerous, spatulate, usually in two series. Total number of segments present about fifty-one, a few of the most caudal being lost.