564 PROCEEDINGS OF THE ACADEMY OF [July, 



like the succeeding thoracic tufts, of two kinds. A few of the 

 dorsahiiost are capillary, more or less sigmoidly curved and narrowly 

 winged. The ventral ones, more numerous and arranged in several 

 parallel rows, are of the mucronate-spatulate type, but have a 

 somewhat narrower and longer obovate blade than those on the fol- 

 lowing somites. On remaining thoracic somites the setre are more 

 numerous, the capillary (fig. 15) forming a projecting tuft, the spatulate 

 (fig. 17) in more and longer rows and having somewhat shorter and 

 broader blades than those on the collar; the mucronate tip is long and 

 slender. Abdominal setse are in two vertical rows, 9 or 10 in each row 

 of the first few fascicles and 4 or 5 in the less distinctly 2-ranked 

 fascicles of the caudal end. Both kinds have the shaft abruptly bent 

 just beyond the surface of the body, the longer form with a very 

 narrow accessory wing on the concave side and a wider but very 

 short wing on the convex side, and the smooth acute tip often 

 much longer than in the seta figured. The short setae (fig. 16) are sig- 

 moidly curved, have shorter, smooth tips and broader, strongly stri- 

 ated wings reflexed from the convex side. 



Thoracic tori bear avicular uncini in the posterior and pick-shaped 

 setae in the anterior row. The former (fig. 18) have long straight bodies, 

 moderate-sized breasts, rather short, erect necks, enlarged heads, 

 prominent 'crests very low in front, and curved beaks. On the last, 

 and possibly other posterior, thoracic somites the uncini (fig. 19) are 

 very much larger, with very long bodies, minute breast, long neck 

 well sloped forward, head not enlarged, very small crest and weak 

 beak. Another less typical one with somewhat larger crest is shown 

 in fig. 20; 43 occur in the 9th and 60 in the 4th torus, though the 

 latter occupy twice as long a space. The pick-shaped setae have 

 the form shown in fig. 22, the heads being much reduced and the 

 hoods much inflated and with slender tips about as long as the beaks 

 of the uncini. Abdominal aviculae (fig. 21) are much smaller than 

 the thoracic, with relatively shorter bases, larger breast, short thick 

 neck, and crest larger, farther forward and extending low down on the 

 beak, which has a straight profile. 



One specimen only known, from station 4,267, off Cape Edgecumbe, 

 Sitka Sound, 922 fathoms, on a bottom of soft gray mud. 



Pseudopotamilla splendida sp. nov. PL XXXVII, figs. 23 to 27. 



This large handsome species is founded on two specimens lacking 

 the posterior end ; wdth the 37 anterior segments alone the type meas- 

 ures 65 mm. long, 27 mm. belonging to the branchiie and 8' mm. to the 

 thorax including the collar, -while the greatest T\idth of the thorax, 

 exclusive of the setae, is 5 mm. 



