128 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 25 



The thorax consists of 14 setigerous segments. The first 2 thoracic 

 notopodia are smaller than others and have no neuropodial branch. The 

 first one is smaller than the second, and the latter is about half as large 

 as the third notopodium. Setae of the first 2 segments are in smaller 

 fascicles than those farther back. The third setigerous segment is the 

 first uncinigerous one. Segments 3 to 9 are ventrally crossed by broad 

 glandular bands. The body tapers gradually thereafter and the glandular 

 shields are absent after segments 12 to 14. 



Thoracic uncini are not unusual ; the cutting edge is provided with 

 4 larger and one much smaller basal teeth (PI. 34, fig. 4). 



Ampharete labrops is unique in having numerous dispersed eyespots 

 along the margins of the large upper lip. The branchiae, numbering 4 

 pairs, are prolonged and slender. The species is unusually small for the 

 genus, and has its distribution seemingly limited to the very shallow, 

 sandy shelf of southern California. It is associated with many other 

 kinds of polychaetes, including Diopatra ornata Moore in kelps, Medio- 

 mastus calif orniensis Hartman, other capitellids and Prionospio spp. 



Family TEREBELLIDAE 



Genus Streblosoma Sars, 1872 



Type S. bairdi (Malmgren) 1866 



Streblosoma crassibranchia Treadwell, 1914 



Plate 14, figs. 5-8 



Collections. Many individuals come from offshore areas in southern 

 California, in silty and mixed sediments. 



Thoracic segments vary from 18 in smaller to 31 in larger individuals. 

 The posterior end of the thorax is abruptly narrowed at the first un- 

 cinigerous segment. The peristomium has many eyespots. A broad glandu- 

 lar shield crosses the ventrum of 6 postbranchial segments. Numerous 

 filiform branchiae are present on setigerous segments 1, 2 and 3; they 

 form tufts, the number of filaments increasing from about 9-10 in the 

 first, to 13-14 in the third branchial tuft. 



Uncini are first present from the fourth (= first postbranchial) seg- 

 ment. They have a characteristic structure (PI. 14, figs. 7, 8) ; a large 

 fang is directed downward abruptly to the plaque, and surmounted by 

 3 teeth in a transverse row. Abdominal uncini (PI. 14, figs. 5, 6) are 

 similar but somewhat broader ; the arrangement of the distal teeth is the 

 same. 



