POLYCHAETOITS AXXEIJDS FKOM CHINA — TREADWELL 265 



effect is that of a dorsomedian dark area covering more than half 

 of the dorsal surface, the pigment being in the form of very fine lines 

 drawn trans versel}^. By the fifteenth somite the lateral margins of 

 this area have become noticeably darker than the remainder. This 

 pigmentation continues tliroughout the greater part of the body but 

 later gradually disappears. The appearance of the hving animal 

 must have been considerably affected by the pigmentation of the 

 elytra. The first two of these rem.ain and are colorless and trans- 

 lucent. Most later ones are lost, but the eighth remains, and in tliis, 

 while in general the translucence remains, there is a patch of pigment 

 extending from its base halfway to its outer margin. The elytron is 

 sufficiently translucent to produce an oceUated efl'ect by the colorless 

 outer end of the elytrophore, boimded on its inner margin by a 

 pigmented band. 



The elytra are all nearly circular in outline and have perfectly 

 smooth margins. They occur throughout the body, at first alternat- 

 ing with cirri but posteriorly several cirrus-bearing somites may he 

 between two of the elytron carriers. 



In a parapodiuin the dorsal cirrus (fig. 18, f) is \qty prominent, 

 extending considerably beyond the end of the setal lobe. The 

 notopodium is rudimentary, having an acicula but no setae. The 

 neuropodium ends in two Hps of which the anterior is the more 

 pointed and the longer. Between the hps is a rounded lobe into which 

 the end of the acicula extends. From the dorsal to the ventral part of 

 the setal lobe is a definite change in the character of the setae. Dor- 

 sally there are a few (3 in the one drawn) slender sharp-pointed setae 

 (fig. 18, g) carrying on one margin a row of fine-toothed plates. 

 Just ventral to these are much heavier setae, nearly twice as thick 

 as to shaft, curved toward the ends and bifid at the apex. These 

 also carrj^ toothed plates (fig. IS, A). Yentrally this type of seta 

 becomes smaller, those at the very lower end being hardly thicker in 

 the shaft than the slender dorsalmost setae. The ventral cirrus is 

 small and located at about half the length of the parapodiimi from 

 its base. 



r?/l)e.— U.S.X.M. no. 20113 (Chen no. 32). 



Family ACOETIDAE 



Genus PANTHALIS Kinberg 



PA.NTHAUS PAXAMENSIS Chamberlin 



Panthalis panamensis Chamberlix, 1919, pp. 86-89; pi. 11, figs. 4-S; pi. 12, figs. 

 1-6. 



An incomplete fragment 25 mm long (Chen no. 47). I was unable 

 to find ail the kinds of setae described by Chamberlin as occurring in 



