132 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 22 



setal ridges are about as far from those of the pair as the distance from 

 the ridge to the sides of the body. 



Typical notopodial setae are very fine, short, pale, and as first de- 

 scribed. Neuropodial setae are dark brown, with the anterior ones much 

 coarser than the posterior (based on the setal stumps which alone remain 

 on the specimens). 



I. pluto bears no resemblance to the other two species except that it 

 too is covered with long slender papillae thickly coated with clay silt, 

 forming balls around the papillar filaments. The body is subcylindrical 

 in shape, abruptly narrowed at one end and truncate at the other; it 

 measures 42 mm long by 11.5 mm wide. A most unique feature is the 

 circlet of 20 fleshy processes surrounding a flat cone with a pore near 

 the center. Each process is a tricuspidate structure, with a double row of 

 three elevations in quadrate arrangement, and the outer side slightly 

 wider than the inner one. The surface epithelium, medially beyond this 

 papillated end, is flaccid for about a fourth of the length of the body, 

 and thereafter abruptly heavily papillated. The other end of the body 

 tapers to a narrowed region with a pore at the subdistal end. I have been 

 unable to distinguish which pore is anterior and which posterior. Cham- 

 berlin (1919, p. 403) considered the papillar end anterior and thus oral. 

 The setae, now all lost, were described as long, heavy, flattened along 

 their length and moderately curved at the tip. 



I. hirsutus Monro (1937, p. 304) was described from the South 

 Arabian Sea in 3385 meters. It is shaped like an Echiurus and is densely 

 covered with long, cirriform papillae. Segmentation is revealed only by 

 the serial arrangement of the setal bundles. 



I. coronatus Monro (1939, p. 130) was named from the Antarctic 

 Ocean in 1266 meters. It measures 42 mm long and 7 mm wide for 18 

 setigerous segments. The body is flaccid and sacklike, externally covered 

 with long, cirriform papillae, and coated with mud. A cephalic cage is 

 formed by setae of the first setigerous segment and these setae are about 

 half as long as the body. The setae of the second segment are also pro- 

 longed and form part of the cage. This species has a pair of massive 

 grooved palpi and about 10 thick, cylindrical branchiae (extruded from 

 the oral cavity). Notopodial setae are slender, cross-barred and capillary. 

 Neuropodial setae are shorter, thicker and obliquely striated, and end in 

 long, tapering tips; some are ornamented with rows of thick hairs near 

 the tips. 



