Benham. Somt New Zealand Polychaetes. 165 



and when these are removed — they only too readily fall away when touched 

 -it is found that they spring from a crescentic platform, which passes round 

 within the collar from one lateral line to the other, outside the palp (fig. 4). 

 In some cases the upper surface of the platform is nearly flat ; at others 

 this surface is directed inwards,' and lies nearly in a vertical plane, due to 

 the retraction of the apparatus. In one case in which the platform was flat 

 I counted the bases of the tentacles : these are arranged in 4 concentric 

 rows ; the outermost, longest, presented about 20 attachment-spots ; the 

 next row 15 ; then 8 ; and the innermost 5. All these rows commence 

 close to the dorsal mid-line, but only the two outer rows extend laterally 

 outside the palp. 



The dorsal median tentacle, or " lingula," is a greyish structure, grooved 

 on its upper surface (really its inner face when not projecting outwards) ; 

 it is a median thickening of the tentacular platform, beyond which it 

 projects as a tongue-shaped organ, and is much wider than a branchial 

 tentacle, and, unlike that, not readily detached. 



The extent to which the " lingula " is visible depends on the state of 

 preservation and consequent degree of contraction of the head organs. 

 When these are strongly contracted and the whole head retracted it is 

 almost impossible to detect the " lingula " without recourse to dissection. 



Traced inwards this " lingula " is seen to pass on to the central or 

 cerebral region of the prostomium, on which are two large pigment patches 

 (? eyes) of variable size and irregular form. Beyond this again, towards 

 the ventral surface, spring the pair of palps, which are longer than the 

 tentacles, grooved on the ventral surface, with the lateral margins crinkled 

 and overhanging. This groove leads into the mouth. 



Following the peristomium, with its crown of chaetae, is a couple of 

 chaetigerous lobes on each side, notopodium and neuropodium, directed 

 forwards ; these carry long capillary chaetae, which lie close alongside the 

 crown. In the following segments the notopodium carries similar chaetae, 

 but the neuropodium carries a hook. 



The next two bundles of capillaries are also directed forwards. The 

 notopodial and neuropodial lobes are short but distinct columns, the 

 former provided with chaetophoral lips. 



The notopodial chaetae are usually about 5 or 6 in number, which may 

 be increased to 9 in the anterior bundles, but all are not of equal length 

 or thickness ; in the more posterior feet about four longer and one or two 

 shorter. These chaetae are long, slender, and beautifully iridescent, rather 

 brownish in colour when seen under the microscope, but on the body (seen 

 by reflected light) are of a pale yellow, or silvery brass colour. They are 

 finely and closely striated longitudinally, and crossed at intervals by distinct 

 lines. Towards the apex these intervals are very long, but as the base is 

 approached the lines become very close together. 



The peristomial chaetae have the same appearance and structure, but 

 differ in that the joint-lines are farther apart at the apex ; the longest of 

 them are about twice the length of the notopodial chaetae of the body- 



The neuropodial hooks are solitary ; only here and there in any of the 

 worms do I find a second hook, either of equal length or only just protrud- 

 ing beyond the surface. 



Viewed under a lens they are shining silvery yellow, with a dark-brown 

 hook-shaped end, bent at nearly a right angle to the shaft, which projects 

 far out of the body in all the specimens. 



