Length, 42 mm.; width to end of setae, 14 mm.; to end of parapodia, 10.8 mm.; exclusive of parapodia, 7 mm.
Taken on Laguna Beach at Mussel Point (Hamilton coll.).
Among other forms known from the California coast characterized especially by the strong tuberculation of all the elytra. The tubercles are mostly large and conical though some are rounded and are confined chiefly to the mesocaudal half and median region of each elytron, a series of large ones ordinarily present along the caudal and caudomesal margin; in the first two or three pairs of elytra the tubercles of the median region especially large, the tubercles on the first pair occurring on the anterior part as well; ectal margin of elytra strongly fringed or ciliate. Elytra in general subcircular but with margin of ectocephalic side flattened or in part a little incurved. Elytra in contact or nearly so at median line but not there at all overlapping. Pairs of elytra eighteen, these being present on somites II, IV, V, VII, IX and so on alternate ones to XXV and then on XXVI, XXVIII, XXX, XXXI, and XXXIII. The last three setigerous somites bear notocirri. Anterior pair of eyes near middle of length of prostomium proper, larger than posterior pair which are a little closer together and are well removed from the others. Lateral prolongations of the prostomium in front which bear the lateral tentacles only a little shorter than the median ceratophore though much more slender. Median tentacle shorter than the palpi, moderately enlarged and strongly rounded subapically and with the usual slender tip or filament which is comparatively short. The lateral tentacles of similar form but much shorter and more slender. Neurocirri of first normal segment large, resembling a notocirrus. The other neurocirri much shorter, subconical, constricted at base and prolonged into a slender but short tip; attached near base of neuropodium in each case. Anal cirri similar to notocirri but much longer and stouter. Neuropodial setae of usual general form, amber colored with dark tip, arranged mostly in two or three, usually uneven, subvertical series. The notopodial setae fine, numerous, the longer ones not falling much short of or reaching the ends of the neuropodials. The nephridial papillæ occupy the ordinary position; they are small and unusually short. The color of the elytra uniform greyish brown. Antennæ, tentacular cirri and notocirri banded at base and distally with black.