410 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



projects from the fascicle. Abdominal neuropodia are similar throughout 

 in that they are provided with only hooded hooks ; the ridges in anterior 

 and median segments are longer and less conspicuously raised than those 

 farther back, but the change is gradual. 



There are no special parapodial respiratory organs, but in life the 

 blood may be observed passing in and out of the long caudal appendage ; 

 respiration may be partly accomplished in this vi^ay. The body tapers 

 gradually and terminates in 2 smooth rings that lack setae; they are 

 followed by the caudal ring and ventral appendage. The anal aperture 

 is dorsoposterior and immediately above the base of the thick, digitate tail. 

 When completely retracted, the tail has the appearance shown in plate 45, 

 fig. 4; in life it is capable of great extension such that its length may 

 exceed that of the last 10 segments. 



Abdominal hooded hooks are unique in having a slender shaft proxi- 

 mal to the node ; they increase in thickness abruptly at the node and again 

 in the hooded portion. The hood is voluminous and has a large aperture. 

 The fang is long, curved, and surmounted by 3 well-separated teeth in a 

 straight transverse series. 



Capitita ambiseta inhabits soft silty mud flats in estuaries where it 

 forms beds. Individuals are surrounded by closely fitting tubes of fine 

 debris and mucus; the tubes are arranged more or less vertically in the 

 upper layers of the silt. In life the individual usually lies head down with 

 tail directed upward; the long caudal appendage projects above the sub- 

 stratum, moving back and forth, presumably for aeration. 



C. ambiseta is associated with several other small annelids, notably 

 Streblospio benedicti Webster, Spiophanes missionensis Hartman, and a 

 tiny undescribed sabellid. From each of these, C. ambiseta can be dis- 

 tinguished in the field by its tube, its characteristic capitellid movements, 

 and its color. 



The generic name refers to the minuteness in size as compared with 

 other known capitellids and the specific name to the dual appearance of 

 pointed setae in both thorax and abdomen. 



Holotype. — AHF no. 119; paratypes in the Allan Hancock Founda- 

 tion. 



Type locality. — Newport Bay, California; in sandy mud banks 

 exposed at low tide line. 



Distribution. — Southern California; intertidal. 



