TUBE OF PANTHALIS. 175 



was swollen up, giving the appearance of a shallow blister 

 about j an inch long ; while ventrally commencing at a 

 somewhat corresponding point the integument rose 

 abruptly, forming a sac over the blood vessel and pro- 

 ducing the effect of a broad longitudinal keel. This 

 portion of the body is capable of very considerable 

 expansion, the advantage of which will shortly appear. 

 In ventral view and outline, the sides of the body, inclu- 

 ding the parapodia, are approximately parallel, the anterior 

 extremity being bounded by a semi-circle, and the posterior 

 by a curve more or less acute according to the elevation 

 or depression of the elytra. Forward, for about ^- of an 

 inch, stretched the two palps, on either side of which the 

 cirri of the first pair of parapodia (as antennae) were 

 sometimes visible ; and between the palps, rising from the 

 under-side of the eyestalks, two small tentacles ; while, 

 with a lens, the tip of the small median prostomial tentacle 

 could also be seen. About -^ of an inch from the extreme 

 anterior boundary of the prostomium, are situate the two 

 buccal bristles or tentacles, one on either side of the 

 mouth, which appears as a short longitudinal line extend- 

 ing forwards between these tentacles. This line indicates 

 the depression, into which the integument folds in graceful 

 curves from every direction, when the proboscis is retrac- 

 ted. Just in front of the buccal tentacles, occupying the 

 space between these and the bases of the palps, come 

 the ventral and dorsal lobes, of the second pair of para- 

 podia, or as I propose calling them the "weaving feet." 

 Centrally situate, at a distance of about ^\ of an inch 

 behind the bases of the buccal tentacles, the dark red 

 ventral blood vessel was a most conspicuous feature. Its 

 front boundary was square and broad, about T V of an inch 

 wide, but the vessel was rapidly reduced in size, and after 

 a course of say half an inch, ran as a moderately fine red 



