SABELLIDES AND SERPULIDES 231 



by a stout peduncle to the dorsal end of either branchial lobe ; second- 

 ary one, when present, somewhat club-shaped, attached to the oppo- 

 site lobe by a more slender, shorter stem. 



Number of segments about 320, of which 7 belong to the thorax, on 

 which the fascicles of setae form very oblique series ; abdominal seg- 

 ments short, the lines of uncini closely crowded. 



Fascicles of seta on the thorax tubular in form ; the first well for- 

 ward on the collar, smaller than the succeeding ones, and directed for- 

 ward ; the others, directed obliquely backward, vary slightly in size, 

 become flattened and laterally elongated. The setae are of two forms ; 

 on the collar slender capillary superior ones and stout bayonet-shaped 

 inferior ones, spinous at the base of the blade (pi. xxxni, fig. 31), on 

 the other segments capillary only ; uncial plates with 6 to 7 long teeth, 

 apparently in two rows (pi. xxxvn, fig. 31). On the abdomen fas- 

 cicles of the characteristic short flaring-ended setae, and on the caudal 

 region other small fascicles of very long, slender, stiff spines ; uncial 

 plates similar to but smaller than those on the thorax, becoming thicker, 

 with more rows of teeth in the caudal tori (pi. xxxix, fig. 33). 



In very young animals taken from their tubes, stained, and mounted, 

 the operculum appears club-shaped ; the rudimentary branchiae re- 

 semble flattened strips of membrane with long unequal filamentose 

 ends, and are covered by the collar ; no membrane appears along the 

 sides of the thorax; this, however, may be due to the position in 

 mounting. There are about 50 rows of uncini on the abdomen, and 7 

 fascicles of setae on the thorax ; the setae themselves are similar to those 

 in the adult. 



A perfect animal taken from its tube is 53 mm. long besides the 

 branchiae, which are about 8 mm., 7 mm. broad on the thorax, and 

 5.5 mm. on the abdomen. A larger imperfect one is 8.5 mm. broad 

 on the thorax and 7 mm. on the abdomen. Diameter of operculum 5 

 to 7 mm. Another specimen, having about 190 segments, 30 pairs of 

 branchiae, and one operculum, is about 35 mm. long and 5 mm. broad 

 on the abdomen. 



Their tubes are thick, white, calcareous, variously twisted, more or 

 less free, the surface of attachment flattened, the exposed surface often 

 roughened by the small tubes of their own young, and also by species 

 of Spirorbis and Hyalopomatopsis. 



Prince William Sound, at Orca, June 25 and 26, two specimens ; at 

 Virgin Bay, June 27, ten specimens. 



Serpula jukesii Grube 1877 (non Baird 1865) closely resembles 

 this species. 



