Length, 23 mm.; width exclusive of parapodia, 3 mm. A little narrowed cephalad, somewhat more so caudal.
Taken at Laguna Beach under stones. (1917)
Body strongly and continuously narrowed caudad. Prostomium wider than long, deeply bilobed, the median tentacle inserted deeply in the intervening incision. Lobes extended forward into peaks which, however, are constricted at base so as to give appearance of more or less distinct ceratophores, these short. Anterior eye free on each side, the caudal one much farther mesad and overlapped by the peristomium. Tentacles short, the median line a little longest and about equalling the palpi; in each a slender tip above the moderate subdistal swelling about equal in length to the remaining part of the style. Tentacular cirri similarly formed, as is also the first neurocirrus, the latter less clavate below the slender tip. Other neurocirri much shorter, shortly subfusiform with filiform tip short; characteristically inserted almost precisely at middle of length of the neuropodium. Notopodia reduced to small lobes at base of neuropodia above, these lobes smooth, bearing no emergent setae in the type. In the average neuropodium the setae are mostly six in number; these are coarse, with subhastate heads the tips of which are curved, entire, and acute; the surface appears smooth, the seriate spinules being exceedingly minute and easily overlooked; pale straw colored. The notocirri have the usual enlarged distal end baring a slender tip and a little exceed the neuropodial setae. The elytra have an arrangement in general similar to that normal in Halosydna so far as that usually goes, but twenty-four pairs are present, these occurring on somites, II, IV, V, VII, IX, XI, XIII, XV, XVII, XIX, XXI, XXIII, and XXVI, XXVIII, XXIX, XXXI, XXXIII, XXXV, XXXVII, XXXIX, XLI, XLIII, XLV, and XLVII. The elytra are characteristically widely imbricated so as completely to cover the dorsum and prostomium. They extend out far laterally so as wholly to overlap the parapodia proper though the ends of the setae and notocirri extend beyond the edges. The elytra have the surface wholly smooth and the edges are also not fringed. As preserved, the type has no definite color markings; color greyish, the elytra of weak fulvous cast.