122 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 22 



fourth has a heavy brown spine (Plate 10, fig. 4) in which a heavy core 

 extends through the distal end. 



The 2 segments of the middle region (= segments 10 and 11) are 

 short and have aliform parapodial processes. The first one conceals much 

 of the dorsal side of the ninth segment, and the second one partly covers 

 the one in front. Their notopodia are deeply trilobed, foliaceous, and the 

 uppermost lobe carries the deeply embedded acicular setae and extends 

 across the middorsum as a thin membranous fold. The aliform lobes of 

 segment 10 are broader though slightly shorter than those of 11, but 

 similar in other respects. In both these segments, the upper and lower- 

 most lobes are the largest and the smaller, middle lobe is a lateral process 

 originating from the uppermost. A heavy flange of cilia separates the 

 uppermost from the lower division. A small round lobe or lateral organ, 

 separates the notopodium from the ventrolateral neuropodium. The 

 uncini are in transverse series, number nearly a hundred in a parapodium. 

 Each is a thin, approximately triangular plate with a finely dentate 

 margin in which the serrations number about 50 and the basal tooth is 

 the largest (Plate 10, fig. 5). 



The third body region differs abruptly from the second one in having 

 parapodia consisting of slender, erect notopodia and low, transverse 

 neuropodia without winglike processes. The first is only slightly longer 

 than the second segment and others are similar to the second. The tall, 

 slender notopodia are at the level of greatest constriction between suc- 

 cessive segments, and the transversely divided neuropodial ridges are on 

 the ventral side of the inflated part of the segment. Notopodia are directed 

 dorsolaterally and terminate in a small knob ; they are penetrated by 2 

 or 3 slender rodlike setae which project from the tip for a short distance. 

 Neuropodia consist of low ridges with transverse series of uncini like 

 those in middle segments, but smaller. 



Phyllochaetopterus lim'icolus differs from other species of the genus, 

 in which the middle region of the body consists of only 2 segments and 

 the modified fourth segment has single large spines, in that the anterior 

 region consists of only 9 segments. 



It has been found most abundantly in San Pedro and Santa Monica 

 Basins, associated with a serpulid, Protis pacifica (see below), and a 

 pelecypod, Cyclopecten zephyrus Grau, but the largest or best developed 

 specimens occur at sill depths or above. 



