POLYCH^TA. — BENHAM. 13t> 



The peristomium is nearly twice the length of the next 

 segment, dorsally smooth but ventrally pleated lengthwise ; 

 whereas the sides are infolded in this individual, they are, in 

 specimens from New Zealand, much longer than the ventral 

 region, and expanded to form a hood or collar which projects 

 outwards and forwards as a longitudinally folded membrane, 

 evidently very mobile in life. 



Its appearance is well seen in the figure given by Johnson^ 

 (PI. iv., fig. 46) of N. cyclurus from American waters. 



The peristomial cirri are short and approximately of equal 

 length, the uppermost is longest, reaching to the 2nd chaeti- 

 gerous segment. 



The parapodia are relatively long, especially in the posterior 

 region of the body. 



The dorsal cirrus, on the anterior feet, is rather more than 

 twice the length of the dorsal ligule (PI. xlvi., fig. 17), but by 

 about the 35th foot it only exceeds it by a little (PL xlvi., fig. 

 18), and in the 50th ancl following it only about reaches to 

 its apex. This relation is retained for the remainder of the 

 body (PI. xlvii., figs. 19-20). The actual length of the cirrus 

 decreases, it is not merely relatively shorter. 



The base of the notopodium just w ithin the cirrus is, already 

 in the 15th segment, quite noticeably elevated, and by about 

 the 20th is elevated and compressed laterally to form a 

 lamella. In the 30th this becomes much higher and continues 

 to do so posteriorly. Meanwhile the dorsal ligule, which is 

 at first a rounded lobe (PI. xlvi., figs. 14-15), soon becomes 

 pointed, elevated and compressed to form a lamella, so that 

 the two structures, over the greater part of the body, unite 

 to form a conspicuous lamella on the upper edge of which 

 the dorsal cirrus is implanted in a slight notch (PI. xlvi., fig.. 

 18). The entire lamella is vascular and glandular, and 

 especially the ligule. 



In the 9th foot (PI. xlvi., fig. 16) the middle hgule is a 

 rounded, conical lobe, shorter than the dorsal, Avhich diverges 

 upwards from it. The ventral ligule is still shorter than the 

 middle and even less than the lips of the ventral chsetophore. 



As wiU be seen from a comparison of the figures of successive 

 feet a line taken along the outer margin of the hgules, which 

 is at first nearly vertical comes to slope downwards and 

 inwards, forming a greater and greater angle with the vertical 

 till in the hinder feet it is about 70°. 



1. Johnson — Proc. Boston Soc. Nat. Hist., xxix., 1901, p. 400. 



