40 AUSTRALASIAN ANTARCTIC EXPEDITION. 



It occurs in each case in company with H. spinosa, but in much less numbers. 

 For example, whereas at 15-20 fathoms fourteen specimens oiH. spinosa were obtained, 

 there was only one of H. tuberosa ; at 25 fathoms, in contrast with sixty-five specimens 

 of the former, there were only fifteen of the latter. Although Ehlers originally 

 regarded it as a variety of H. spinosa, since it seems nearly always to occur in 

 association with it, yet in his later work he pointed out that it is a very distinct species. 



There are one or two features which readily serve to distinguish it at sight from 

 H. spinosa: (1) The dorsal chgetge, instead of projecting outwards, have a radiating 

 arrangement, as is shown by Ehlers's figure ; (2) The absence of pigmentation of the 

 upper lip and of the ends of the parapodial lobes (" acicular processes ") which is practi- 

 cally universal in H. spinosa. 



The dorsal surface of the body is free from pigment, so far as my observations 

 go, but the lateral longitudinal ridges along the ventral surface are crossed by bars 

 of brown, and the posterior feet may be pigmented on their lower faces. The ventral 

 surface thus appears dark. 



Ehlers has directed attention to the peculiar transverse " pads " which occupy 

 the median line of the dorsal surface in each segment, and the " cushions " on the 

 cirriferous segments in line with the elytrophores, the cirrophores being situated far out 

 on the bases of the parapodia. Both these structures occur also in the genus 

 Physalidonotus, which Ehlers founded for a Branchiate Polynoid from New Zealand, 

 in which the head, however, is " lepidonoton." Having had several species of this genus 

 under examination recently, it occurred to nae that possibly there might be gills here 

 also, but on investigation I find tluit they are absent. 



The dorsal chpetse are " bearded " in the same sort of way as are those of 

 Physalidonotus. It is evident that Ehlers had before hina and has figured a much-worn 

 chseta, and that he failed to recognise the true nature of this " bearding," for he 

 writes, " ich mag nicht entscheiden, ob diese Faden durch Aufsplitterung des 

 Borstenendes entstanden oder epiphytische Bildungen sind." 



To me neither of these explanations of the appearance presented by the chsetse is 

 the correct one. These long " Faden " are similar to those originally figured by Moore 

 (1903) for certain species, which he named Lepidonotus brancJdferus and L.chitoniformis 

 (pp. 405, 409, pi. XXIII, figs. 7 and 10), which really belong to the genus Physalidonotus. 

 More recently I have figured the chtetse for P. rugosus and P. paucibranchiatus (Benham 

 1915, pL XXIX). 



A more detailed account of the dorsal chsetse oiH . tuberosa is, therefore, desirable. 

 In a perfect unworn chseta the tip is smooth and rather bluntly pointed. Below this 

 smooth region there come three or four pectinated frills* which are produced into long 



* Tills term was used by A. G. Bourne in liis account of the chsetse of Lep. claim. (Trans. Linn. Soc. London., vol. ii, 

 1S83.) 



