NO. 3 HARTMAN : ORBINIIDAE, APISTOBRANCHIDAE, PARAONIDAE 307 



The thorax consists of 13 or 14 setigerous segments with the transi- 

 tion abrupt thereafter ; it is most noticeable through the change in neuro- 

 podial setal fascicles. The first three setigerous segments differ from 

 those farther back especially for the presence of brush-tipped (fig. 2) 

 setae with a thick stalk. The third parapodium has a slender postsetal 

 notopodial lobe and a similar though thicker lobe in the neuropodium 

 (fig. 1). The notopodial fascicle consists of many slender setae extend- 

 ing distally in fan-shaped series. The corresponding neuropodium has 

 setae of two abruptly different kinds. Most have a brushy tip of which 

 some are finer (fig. 2), others coarser (fig. 3) ; about eight others are 

 slender and capillary, in a close tuft at the superior end of the series. 

 The largest brush-tipped setae are behind and below the smaller ones, 

 in a series of 14 to 20, and in line with the postsetal lobe; the anterior- 

 most series number about 24 in a row. The shaft of the smaller ones is 

 more strongly transversely ridged but otherwise similar. 



Parapodia of more posterior thoracic segments have postsetal lobes 

 that are very long, slender and similar to one another. Their setae are 

 of a single kind, slender, distally pointed, with transverse serrations 

 along the outer exposed part. Notopodial acicula are pale yellow and 

 number several in a close sheath. 



Branchiae are first present from the eighth setigerous segment ; the 

 first are small, slender and tapering; farther back they increase in size 

 but are nowhere conspicuous. They are simple, entire lobes with an 

 occasional one abnormally bifid ; their lateral margins are inconspicuously 

 fimbriated. In some individuals there is a diminution in size, so that in 

 far posterior segments the branchiae are very small ; in others they are 

 long and slender, exceeding in thickness and length their accompanying 

 notopodial postsetal lobe. Branchiae of a segment are widely separated 

 middorsally ; a fleshy welt-like ridge is continued across the dorsum be- 

 tween the branchial bases, but seemingly lacks fimbriae. 



Thoracic neuropodia have a short to long postsetal lobe located at 

 or near the midlength of the postsetal ridge. It is shortest in front and 

 increases posteriorly to a long, tapering cirruslike lobe in both notopodia 

 and neuropodia. 



Abdominal neuropodia have a prolonged base extending far beyond 

 the corresponding notopodia. The distal end is bifid, comprising a 

 rounded presetal (or superior) part and a slenderer, equally long post- 

 setal (or inferior) lobe. A single yellow aciculum extends to the end 

 of the neuropodium or slightly emerges from the lower edge of the pre- 

 setal lobe; one or two very slender capillary setae accompany the acicu- 



