258 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 15 



Total length of mature individuals is 80 to 90 mm ; segments num- 

 ber to about 300. The thorax has 16 to 19 (pi. 21, fig. 1) setigerous 

 segments. Transition from thorax to abdomen is abrupt and involves 

 one to three segments; it is marked by an abrupt change in parapodia 

 and the appearance of ventral fringe. Epithelial welts nearly encircle 

 the body (preserved) in the thorax. The prostomium is about twice as 

 long as broad and tapers anteriorly to an acute tip (pi. 21, fig. 3) ; eye- 

 spots are absent, at least in mature individuals. A pair of nuchal organs 

 occupies the posterior lateral position. In individuals from a single col- 

 lection the peristomium may be only one-third as long as the prostomium 

 or it may exceed the latter in length. The eversible proboscis is a much 

 folded epithelial sack. 



Branchiae are first present from setigerous segment 15 or not before 

 20. The first branchiae are small and they gradually increase in size on 

 the next five to ten segments, becoming erect and lanceolate in shape. 

 When fully developed they have conspicuous ciliated marginal fringe 

 and taper distally to a smooth tip (pi. 21, fig. 4) ; they are simple and 

 unbranched throughout. 



In the thorax the postsetal lobe is simple, small or inconspicuous in 

 notopodia and neuropodia (pi. 21, fig. 1). In neuropodia a simple lobe 

 is located at the middle of a long, low fleshy ridge; it is only slightly 

 thicker than the notopodial postsetal lobe. At about segment thirteen, or 

 where the fringed region begins, the notopodial lobe elongates and gives 

 rise to the dorsal postsetal lobe farther back. At the same place the 

 neuropodial lobe increases in size. 



Ventral fringe is first present on segment 17 or not before 19 or 20 

 and is continued back through 12 to 14 segments (pi. 21, fig. 1). It 

 begins as a pair of elongated lobes on the ventrolateral side of the body ; 

 on the next few segments there are 3 or 4 to 9 pairs of lobes forming a 

 continuous series across the ventral side of the body. Thereafter there is 

 a gradual diminution of lobes to only one on the thirty-third or follow- 

 ing segment. 



Neuropodial ventral pads in the abdomen are foliaceous, entire 

 ridges, most conspicuous in sexually mature individuals when they are 

 crowded with gonadial products, at which time they are thick and in- 

 flated at the base. These pads are first present, though small, where the 

 ventral fringe disappears; they gradually increase in size and length. 



Thoracic neuropodia are elongate oval ridges with a small papillar 

 lobe at their midlength. Abdominal neuropodia consist of two lobes, of 

 which the upper one is longer and thicker than the lower one (pi. 22, 



