292 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 15 



The prostomium is longer than wide and only slightly depressed; 

 there are no visible eyes. The nuchal organs are large, transversely 

 oval invaginations at the sides, located near the anterior margin of the 

 peristomium. The proboscis, partly everted in some individuals, is a 

 large vesicular pouch. Only the first segment is a simple, smooth ring, 

 longer than the first setigerous segment and narrower. Transition from 

 thorax to abdomen occurs at setigerous segments 15 to 18. Parapodia of 

 the first 12 segments are lateral; thereafter they shift upward and be- 

 come dorsal in the abdomen. 



Branchiae are first present on the eighteenth setigerous segment and 

 are thus entirely abdominal. The first pairs are slender, digitate simple 

 lobes, located at the dorsal base of the notopodium, leaving a wide mid- 

 dorsal space bare. They are visibly fimbriated at their lateral margins. 

 Farther back they slowly increase in size. At about segment 80 there is 

 an occasional divided branchia but many segments continue to have 

 simple ones. In the posterior half of the body the branchiae rapidly 

 divide dichotomously so that in the posterior fourth of the body they are 

 all branched, with as many as six terminal filaments (fig. 2) ; together 

 they form a dense mass of filaments over the dorsum of the body. 



Parapodia from the first segment are well developed but there is a 

 gradual increase in the development of neuropodial fascicles to about 

 segment ten, after which the fascicles diminish through segments 11 to 

 15 and gradually become more limited. Notopodial and neuropodial 

 postsetal lobes from the first segment are long, triangular; in middle 

 thoracic segments they are foliaceous (fig. 1) with the neuropodial one 

 the larger. The third thoracic notopodium has a digitate postsetal lobe 

 and about 12 pointed setae, with the longest ones in the upper part of 

 the fascicle. Each seta is distally tapered to a point and closely barred 

 along its length. The corresponding neuropodia have a shorter postsetal 

 lobe; their setae are similar but shorter, with the longest ones in the 

 upper and lowermost positions in the fascicle; in addition there are 8 to 

 14 uncini in a single series, located in the anterior and inferior part of 

 the fascicle in a line approximating the shape of a printed letter J, with 

 the long end of the letter at the anterior end and the short one at the 

 posterior end. The uncini are distally blunt, slightly curved and have 

 no hood; at their outer curved region they are closely but vaguely pec- 

 tinated. Other thoracic parapodia resemble those of the third segment 

 but are larger as far as the eleventh to fourteenth segment, after which 

 there is a gradual diminution. By the eighteenth segment there are only 

 about seven uncini in a neuropodial fascicle, accompanied by a small 

 number of pointed setae. 



