POLYCHAETOUS ANNELIDS FROM CHINA — TREADWELL 267 



where it is 8 mm in diameter. Throughout the rest of the body the 

 diameter is somewhat less than tliis, and at the pygidium there is an 

 abrupt narroAving. 



The prostomium (fig. 18, i) is distinctly bilobed, the dorsal longi- 

 tudinal depression extending about halfway to the peristomiai border. 

 The outer right tentacle iias been lost, but the others are all about of 

 the same size, only a little longer than the prostomium. Setigerous 

 somites 2 to 4 are all of about the same length, about half that of the 

 peristomium. Later ones are about half as long as these. In the 

 preserved material the body color is brown with marked iridescence. 



The first parapodium (fig. 18, j) has its setigerous portion a little 

 posterior to the bases of the dorsal and ventral cirri and carrying a 

 prominent bundle of compound setae, which extend beyond its dorsal 

 and ventral surfaces. There are three heavy aciculae. The dorsal 

 cirrus is about twice as long as the setal lobe, its apex bluntly rounded. 

 The ventral cirrus is about three-fourths as long as the dorsal but is 

 broader and its apex blunter. In the tenth parapodium (fig. 18, k) 

 the setal lobe is relatively larger than in the first and is in the form of 

 a rounded lobe from whose anterior face a tuft of setae extends dorsally 

 and ventrally as well as along the face of the lobe. The dorsal and 

 ventral cirri are, relative to the setal lobe, much slenderer than in 

 the first but retain their relative sizes with respect to one another. 

 Aciculae make up a dense black mass in the setal lobe, coming to the 

 surface among the setae. The ventral setae of the setal tuft are com- 

 pound, the dorsal one simple, and the ventralmost ones are quite 

 short, while those at the top of the bundle extend beyond the ends 

 of the dorsal cirrus. A parapodium from the middle of the body 

 (fig. 18, I) lias a less prominent setal lobe than is the case in the 

 anterior ones and the setae are fewer in number. The ventral cirrus 

 is an inconspicuous cone attached to the end of a ventral swelling, which 

 is fused for nearly its whole length to the ventral face of the setal lobe. 

 In addition to setae like those found farther forward, there are pecti- 

 nate ones in the dorsal part of the bundle. The dorsal cirrus is a 

 slender cone inserted much above the setigerous portion and attached 

 to the base of the prominent gill. 



In the type the thirtj^-fiJth setigerous somite has one very small 

 gill filament on the left side, but the series really begins on the forty- 

 fifth, and they extend to within about 30 somites from the pygidium. 

 I saw none that had more than three filaments, and posteriorly they 

 have only one. There is one pair of small anal cirri. 



The simple setae are relatively rather heavy in the stem and are 

 long and gently curved to sharp points. Compound ones (fig. 18, m) 

 have the terminal joint long and curved and tapering to sha.rp points. 

 Aside from the jointing the general contours of the two kinds of setae 

 are similar. 



