Barrukia curviseta (Monro 1930)

“Harmothoë (Barrukia) curviseta, n.sp.

St. 181. 12. iii. 27. Schollaert Channel, Palmer Archipelago. 64° 20' 00" S, 63° 01’ 00" W.

160-335 m. Gear OTL. Bottom: mud. One small fragment.

St. 186. 16. iii. 27. Fournier Bay, Anvers Island, Palmer Archipelago. 64° 25' 30" S, 63° 02' 00" W. 295 m. Gear DLH. Bottom : mud. One specimen.

DESCRIPTION. Two fragments, the larger of which is composed of 24 chaetigers and measures 30 mm. by 10 mm. including the feet: the colour is pale yellow in spirit.

The prostomium (Fig. 15, a) is as broad as long and divided by a median groove. The insertion of the lateral tentacles is ventral, but the prostomial peaks are not distinct. The eyes are small ; the anterior pair, which is the larger, is far forward and laterally placed, so that it can scarcely be seen from above. The posterior are about in the middle of their half of the prostomium. The median tentaculophorc is fairly stout and the median tentacle is lost. The lateral tentacles are small and hirsute, and the palps long, tapering and smooth. Laid along the back they rcach to the 5th chaetiger. The tentacular cirri are missing. The first five chaetigers have conspicuous mid-dorsal tubercles, rounded in the first two chaetigers and transversely elongated in the remainder.

Elytrophores are present on the 1st, 3rd, 4th and every alternate segment up to the 22nd; the pseudo-elytrophores are very conspicuous and similar in appearance to the elytrophores. The elytra are dotted throughout with small tubercles with truncated and irregular tops, and except for a small area near the inner border there are long cilia both on the scale itself and along its free edges (Fig. 15, b).

The feet arc biramous : the dorsal cirri are lost, but the dorsal cirrophores are large, dorso-ventrally flattened structures ending in a rounded knob for the cirrus: they lie above the foot, and their end falls just short of the tips of the dorsal bristles.

The mid-ventral edge of the dorsal chaeta sac is carried out to a point containing the aciculum, and the middle of the anterior lip of the ventral chaeta sac is similarly pro­duced. The notopodium appears to have been twisted through a right angle, so that the aciculum is in the mid-ventral line, and the dorsal bristles are arranged in three superimposed rows parallel with the long axis of the body. The ventral bristles lie at right angles to the dorsal.

The upper row of dorsal bristles (Fig. is, c) is shorter than the rest, strongly curved towards the tip, and provided with rows of prominent pectinae on their convex side. The tips are devoid of hairs. Similar bristles are found in Willey's Gattyana cristata from Franklin Island, the genotype of Barrukia. The remaining two rows (Fig. 15, d) of dorsal bristles are lightly pectinated, and end in hairy tips, the "setae penicillatae " of Bergström.

The ventral bristles (Fig. 15, e) are slightly more slender than the dorsal, and in place of the usual rows of teeth, there are two short series of two to three teeth. One of these series is always seen lying along the middle of the shaft and the other to its right side. The arrangement is not unlike that figured by Bergström (1916, Pl. v, fig. 9) for Barrukia cristata. The ventral chaetae are prolonged into very fine delicate flagelliform tips which curl over in the shape of a hook. The extent to which the tips are bent over varies widely and a few bristles are without the curving of the tip. The ventral cirri are very small; they are attached to stout bulbous cirrophores.

REMARKS: I have attributed these fragments to the sub-genus Barrukia on the ground of the presence of dorsal “setae penicillatae.” There are other characters, however, in which they resemble the genotype, the presence of the median dorsal tubercles, the shape of the dorsal cirrophores and of the feet. They differ from Barrukia cristata in the number of median dorsal tubercles, in the presence of long curved flagelliform tips to the ventral chaetae, and in the sculpturing of the elytra.”

(Monro, 1930)