Cbaetopterus \''ariopedatiis. 487 



late plane surface at right angles to the plane of flattening of the 

 notopodia. A complicated ciliary furrow on each notopodinm extends 

 from the proximal end of the spatulate surface along the dorsal 

 margin of the notopodinm, to a mid-dorsal position where each meets 

 the furrow from the opposite side. At this point these furrows unite 

 with the furrow from the anterior region. The worm, when the tube 

 is opened, is frequently found with its aliform notopodia bent ob- 

 liquely forward and dorsalward till the spatulate surfaces join. The 

 large open arch thus formed brings the ciliated furrows into the 

 inner border of the arch where it can serye most effectiyely as an 

 organ for collecting the food. This function will be referred to in a 

 later paragraph on the feeding habits. 



The aliform notopodia are strengthened internally by the presence 

 of numerous straight, slender setie which do not protrude to the 

 exterior except in specimens that haye begun to macerate. They are 

 arranged parallel to one another and oblique to the long axis of the 

 appendage. The yentral rami, or neuropodia, of the twelfth seg- 

 ment, are fused to form an elliptical adhesiye disc which is concaye 

 ventrally. It, together with the adhesiye discs on the yentral side 

 of the next two segments, attaches the animal to the inner wall of 

 the tube. In form and size the disc of the twelfth segment agrees 

 with the adhesiye disc of the thirteenth segment, therefore the descrip- 

 tion of one will answer for the other. The long axis of both adhe- 

 siye discs is equal to or greater than the width of the plastron of the 

 superior region and the width is equal to about half the length. They 

 bear, along their free anterior and posterior edges, numerous brown 

 uncinal plates with serrate edges, as has been well described by 

 LafPuie in tracing out the homologies of the parapodia. Of the 

 structure of these small saddle-like yentral suckers or adhesiye discs 

 Laffuie says (page 261) : "The fusion is indicated by a median 

 furrow which presents a little depression toward its middle." This is 

 especially true for the adhesiye disc of the fourteenth segment (third 

 of the mid-region), but it is not obseryable in the large adhesiye discs 

 of the twelfth and thirteenth segments. Just dorsal to the adhesiye 

 discs are the two large yentral muscles. They extend along the 

 yentral side of the mid-region from the epaulet-like neuropodia of 



