1923] NATUEAL SCIENCES OF PHILADELPHIA 249 



the opercular disk, with a pair of broad, thin wings, occupying the 

 distal three-fifths and ending in a pair of free lobes at the operculum. 

 The opercular disk is attached to the stalk eccentrically and reaches 

 ventrad over the ends of the gills. The disk itself is nearly circular, 

 hard and calcareous, slightly pink in color, with a rough, irn^gular 

 outer surface bearing three irregularly branched slight!}' flexible 

 spines, a fourth having probal)ly ])een lost, and closely resembles 

 that of Potnalocera.s quadricornis (Irube from the Philippine Islands. 



The oral mem])ranes cannot be seen. Setigerous somites: thor- 

 acic, 7; abdominal (incomplete), 86. Peristomium and first setiger- 

 ous somite elongated, the region of the thorax anterior to the first 

 torus comprising one-third of its total length. There are no distinct 

 ventral plates but merely a triangular glandular inter])odal area 

 with the caudally directed apex prolonged into a linear area between 

 the last three or four pairs of tori. Abdominal segments very 

 short and crowded with soft, smooth, dorsal and ventral areas and 

 obscure lateral tori; ventrad to which are minute inconspicuous tufts 

 of setse. 



Collar closely appressed to the branchial bases, thrown into 

 deep folds and produced into dorsal and ventral lobes. The margin 

 is irregular and bears small processes and lobes but no deep fi.ssures. 

 The ample mantle is also closely wrapped round the thorax and 

 much plicated; anterior border produced on each side into a narrow 

 lobe that reaches beyond the base of the opercular wing; its 

 dorsal border rises well above the setse and meets its fellow medially 

 as far back as the fourth pair of setse tufts; ventral transverse 

 fold also wide and overlaps the first abdominal segment. 



The small tufts of collar setae widely sejiarated from those of 

 both the same and the opposite side on the dorsum. Remaining 

 six thoracic tufts large and fan-like, lateral, but becoming succes- 

 sively more ventral. Tori begin immediately ventral to the setse 

 and are very long, the last three pairs practically meeting ventrally. 

 They form thin fiat folds projecting freely caudad and overlapping 

 the bases of the setse tufts dorsally and the venter of the segments 

 ventrally and bear the very numerous uncini on their free mar- 

 gins. 



Collar setiP tufts very small, containing only 8 or 10 very small, 

 simple tapering setae. Other thoracic fascicles are large and 

 conspicuous, of much larger, simple, tapered, curved, limbate and 

 acute setae. Abdominal setse very few and very delicate, with 

 obliquely expanded finely toothed and pennoncd ends. Thoracic 

 uncini (Plate XVIII, fig. 47) very numerous, with eleven acute ap- 

 pressed teeth and one lower blunt and flattened tooth. Abdominal 

 uncini similar l)ut smaller with seven acute and one l)lunt tooth. 



Tul)e known from a few fragments attached to the worm, white, 

 very hard and stony, lumen circular, 2.5 mm. in diameter, the 

 surface more or less pitted and produced into small irregular wings 



