POLYCH.ETA BENHAM. 79 



They are stated to be " red in life," but in the preserved condition, of course, this blood 

 c olour is absent; they are almost white, with the anterior end grey. The dimensions 

 are remarkably uniform, and though most of them are curved, the length of the straight 

 ones is 25 mm., with a breadth of 2-5 mm. at a short distance from the anterior end, 

 whence the body tapers slowly backwards. The hinder end is usually imperfect, and 

 many seem to have this region more or less regenerated. 



The worm contains from 60-109 segments, the last ten or a dozen of which are 

 very small. Many are sexually mature. 



The dorsal surface is flat, the ventral very convex. The prostomium is a short 

 truncated cone ; in many cases quite blunt, in others roundly pointed. It is divided 

 from the large peristorrmim by a furrow, at the anterior margin of which is a pit on each 

 side, and immediately in front of this is a pigment spot. On the ventral surface of 

 this region the large lateral lips are prominent, with a median lip between them. 



The anterior eleven segments bear only the low parapods, with lips and bundles 

 of chaetae. The chaetae are colourless, long, extremely fine capilliforms, with a saw- 

 like edge on one side, which is composed of blunt, rounded teeth; the striae between 

 which do not reach right across the blade. 



The dorsal and ventral chaetse are alike, both in the anterior segments and in the 

 posterior. I find no " forked " bristles, nor " acicula," such as Fauvel describes for 

 his specimens of 8. kergudensis(19lQ),^. 443, pi. VIII, figs. 23-24. Each bundle of 

 chaetse issues in front of a more or less pronounced cirrus, or " lip." The lip of the 

 dorsal bundle is conical in form, that of the ventral is lower and of greater vertical 

 height. In the anterior 12-14 segments the chaetae project laterally, but further back 

 the parapods gradually rise up the sides of the body, so that the chaetae become directed 

 upwards. Each segment behind the 14th is triannulate, the middle annulus being 

 much the larger of the three. 



The gills commence on the 12th segment, and extend almost to the end of the 

 worm, except apparently on the last 10 segments or so, which are very small, and 

 have no outgrowths of any sort. The gills are sub-cylindrical, somewhat flattened on 

 their antero-posterior faces, which increase in length towards the hinder end of the worm 

 till they are nearly as long as the body height. 



In this gilled region the ventral surface of each segment is traversed by a glandular 

 ridge, which commences below the parapod, where it widens out to form a triangular 

 area with the base upwards; in the anterior segments of the branchial region, this 

 dwindles to a small papilla and dies out. 



The position of the gills is remarkably constant : thus in 31 individuals of approxi- 

 mately equal size, taken at random, from various vials representing different hauls, 

 I find that in 17 ot them the gills commence on the 12th segment on both sides; 



