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“Kesun abyssorum, n.sp.
St. 177. 5. iii. 27. 27 miles SW of Deception Island, South Shetlands. 63° 17' 30" S, 61° 17’ 00" W. 1080 m. Gear DLH. Bottom: mud and stones. One specimen.
DESCRIPTION. The body (Fig. 69, a) is acorn-shaped from contraction, and measures 21 mm. for 23 chaetigers. The diameter is 6 mm. at its widest part. There is a very short, blunt, smooth prostomium, followed by a triannulate buccal segment with paired nuchal pits. Apart from the prostornium the surface of the body is granular or finely vesicular; and as described by Chamberlin for Kesun fusus, each annulus is marked by a row of fine but distinct vesicular papillae. There is no trace of gills.
In the anterior portion of the body the bristle bundles arc borne on small papillae, and above and below the foot are one or two papillae much larger than the other papillae of the middle annulus (Fig. 69, b). From about the 12th chaetiger all the papillae of the middle ring increase in size till they equal the papillae lying above and below the foot. Consequently, for the last ten segments, the bristle bundles lie in a deep groove (Fig. 69, c), the sides of which are formed by the annulus in which the feet lie. The terminal segments are uniannulate. The lateral prominences so conspicuous in Travisia are wholly absent.
From the 6th to the 9th chaetigers inclusive, there is on each side below the foot an enormous oval nephridiopore, the vertical diameter of which is about equal to the distance between the bristle bundles. Between the bristle bundles sensory pits are present as in Travisia. The anal cylinder is about equal in length to the last two segments, and faintly longitudinally furrowed.
REMARKS. This form is allied to Kesun fusus, Chamberlin: it differs in the number of segments and in the possession of a deep posterior groove in which the feet lie.”