82 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



that the articulation is more or less distal ; these are accompanied by 3 

 to 5 acute, narrowly bilimbate setae and 4 or 5 fine pectinate setae. In a 

 fifth setiger there are 3 pseudocomposite hooks, of which 2 resemble those 

 in front, but the other is transitional, resembles those farther back (pi. 5, 

 figs. 90, 91) with indications of an articulation. The sixth (first branch- 

 ial) setiger has 4 yellow, embedded neuroacicula and several kinds of 

 setae. Below there are 6 to 7 broad bladed, simple, pointed setae; above 

 there are 4 to 6 longer, slender, though similar, bilimbate setae and 3 or 



4 fine pectinate setae; submedially there are one simple tridentate hook 

 (pi. 5, fig. 97) and a similar, articulated one, continued through setigers 



5 to 9. Composite spinigers are totally lacking, their usual position taken 

 over by simple limbate setae. Between the tenth and sixteenth setigers, 

 where acicular and subacicular hooks are absent, simple, pointed setae 

 occur in a corresponding position. 



Subacicular hooks are present from the seventeenth to twenty-second 

 setiger, and continued to the end. They are distally bidentate, hooded, 

 and differ from those in other species in that the teeth are more prolonged 

 and more obliquely disposed (pi. 5, fig. 93). A median parapodium has 

 2 or 3 yellow neuroacicula, 2 subacicular bidentate hooks, about 10 acute, 

 narrowly bilimbate setae, and a fine fascicle of pectinate setae (pi. 5, 

 fig. 96). 



Branchiae are present from the third or fourth setiger, with one fila- 

 ment, or not until the seventh, with 4 or 5 filaments (pi. 5, fig. 95) in 

 pectinate arrangement ; already here some of the filaments are as long as, 

 or longer than, the respective dorsal cirrus. The number of filaments in- 

 creases gradually, so that there are about 5 on the tenth setiger, 6 on the 

 fifteenth, 10 or 11 on the twenty-fifth setiger (pi. 5, fig. 92), and thus 

 are continued through a long region, though diminishing in size and 

 number of filaments at about the sixtieth setiger. At segment 150 there 

 are still 3 or 4 filaments. The branchial stem usually comes to be broader 

 (pi. 5, fig. 92). 



The maxillary apparatus is delicate, as is usual in the genus. The 

 plates are translucent and horny. The carriers are longer than broad, 

 taper basally to bluntly pointed ends. The forceps are thin, falcate. On 

 the left side maxilla II has 7 teeth. III has 8 teeth, IV has 5 teeth, and 

 V has a single tooth. On the right side, maxilla II has 8 teeth. III has 8 

 teeth, and V has one tooth. The mandibles have long, slender ends, sep- 

 arated for their entire length ; the calcareous plates are oblique and flar- 

 ing. 



O. vexillaria has been reported by Treadwell (1923, p. 8) from 

 Lower California, but it was said to differ from the original account in 



