140 MR T. 7. HODGSON ON THE 



the African coast. Of the Antarctic species, two are identical with species taken by 

 H.M.S. Challenger off New Zealand in 1100 fathoms (Station 168). N. longicoxa was 

 taken in 1410 fathoms, lat. 71 22' S., long. 16 34' W. ; and N. compactum was taken 

 in 1775 fathoms, lat. 62 10' 5" S., long. 41 20' W. The great distance from the point 

 of their original discovery is well worthy of note, as well as the increase of depth. 



Chaetonymphon contains four species with some interesting facts in distribution. 

 C. orcadense is described as a new species, and was taken in Scotia Bay in immense 

 numbers, and a single specimen from the Burdwood Bank, off the Falkland Islands. 

 At first sight it is like C. australe, Hodgson, but is readily distinguished by the distinct 

 auxiliary claws. C. assimile is a new species of which there are many specimens in the 

 collection. This one and C. australe and C. altioculatum, Mobius, are all very closely 

 allied. In my report on the Discovery collection I stated that I was unable to regard 

 C. altioculatum as distinct from C. australe. C. austrinorum I regarded as a variety 

 of C. australe, though a well-marked one. These four species or varieties, whichever 

 they may be, differ more definitely in their setose covering than in any other particular. 

 I have no reason to modify my opinion on their specific differences ; but with regard 

 to C. altioculatum, Mobius, there is most room for doubt. Examination of the type 

 specimens reveals the fact that there is a fringe of small setae at the posterior border of 

 the trunk segments. This feature is not very prominent, and is not brought out by 

 Professor MOBIUS' description ; and if this is not to be regarded as a specific character, it 

 has a certain value when the variation and distribution of species are under consideration. 

 All the other peculiarities of the animal agree closely with those ascribed to C. australe, 

 and one does not feel justified in separating the two as distinct species. No specimens 

 of C. australe or this particular variety occur in the Scotia collection, but a very 

 close relation exists in Chaetonymphon assimile, which is described as a distinct species. 

 It is readily distinguished by the setose character of its body, which is devoid of setae, 

 except for a few long ones as a distal fringe on the lateral processes ; other features 

 show that it may be regarded as distinct, though closely allied. 



An important bond of union between all these species is the tall ocular tubercle, 

 which caused Professor MOBIUS to derive the name of his species from that organ. One 

 specimen of C. assimile and another of C. orcadense have two fairly well-developed 

 eyes on one side of the tubercle, in addition to the four at the summit. 



A purely sexual feature lies in the fact that in C. australe, C. austrinorum, C. alti- 

 oculatum, and C. assimile the ovigers of the adult male all have the fifth joint abruptly 

 expanded to more than double its diameter for its distal half; the following joint also 

 is considerably enlarged, but most so proximally. Another is the enormously developed 

 distal fringe which occurs ventrally on the third coxae of the two posterior pairs of legs 

 in the male. 



C. mendosum is not uncommon in Scotia Bay at 10 fathoms; at the other side of 

 the hemisphere, and farther south by 16, the Discovery found it equally abundant, but 

 only below the 100-fathom line. 



(ROY. soc. EDIN. TRANS., VOL. XLVI., 160.) 



