AMPHIPODA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 193 



modifiefl his original description in one or two points in which he found that the 

 additional specimens showed some slight variation from those at first described. In 

 1903 he also had identified as 0. ahyssorum specimens obtained from the Atlantic 

 by the Oceania. 



The Scotia collections contain an enormous number of specimens from the various 

 localities given above, and a comparison of these with co-types of Walker's species showed 

 that they were the same as the forms described by him under the name O. rossii. A 

 comparison of the different specimens from the South Orkneys and other Scotia localities 

 with co-types of Walker's species supplied by the British Museum, and with specimens 

 collected by the Nimrod Expedition, showed that the species varied greatly not only 

 in size but also in several points which had been relied upon by previous authors for 

 the description of different species — for example, in the second gnathopod, some of the 

 specimens having the palm strictly transverse, while in others it was slightly produced 

 so as to give the gnathopod almost a chelate character ; in the postero-lateral angle to 

 the third pleon, which in some is quadrate and in others more or less broadly rounded ; 

 and in the proportions of the two branches of the third uropods. There are, of course, 

 also differences between the sexes, the males having the lower antenna considerably 

 longer than the females, and having the branches of the third uropod supplied with more 

 numerous long plumose setse, though some similar sette are present in the female. An 

 examination of young forms appears to show that these setae are only developed to the 

 full extent in older specimens, there being fewer in younger forms. 



I was able also to compare these specimens with a specimen of O. proxima 

 Chevreux from Port Charcot, kindly sent to me by Monsieur Chevreux, and I have 

 come to the conclusion that this species is the same as O. rossii, the differences which 

 M. Chevreux points out being accounted for by the variations mentioned above. In 

 the character of the eyes and in other points it is quite the same as a specimen of 

 0. rossii of moderate size ; on the other hand, as M. Chevreux points out, it is con- 

 siderably larger than the forms from the North Atlantic on which he originally 

 described the species O. proxima. From the Vienna Museum I obtained specimens of 

 Anonyx chilensis Heller, taken by the Novara at Chili. This proved to be about half the 

 size of 0. proxima ; it differs a little in the shape of the eye and in the somewhat smaller 

 size of the rounded prominence on the first segment of the urus, but in all other points 

 I can find nothing to distinguish it from 0. rossii Walker. In Anonyx chilensis the 

 eye is almost oval, widening slightly below, and it is colourless in the spirit specimens 

 and probably was red in the living animal, as described by Sars in 0. ohtusa. In large 

 specimens of O. rossii from Antarctic regions, the eye usually differs somewhat in shape, 

 being much narrower above and wider below, and in most of them it is dark in colour 

 in spirit specimens, though in many, and especially in forms preserved originally in 

 formalin, there is still a reddish tinge to be seen. Moreover, even in the Antarctic 

 specimens there is some variation in the size, shape, and colour of the eyes, and conse- 

 quently I do not think this slight difference sufhcient to distinguish Anonyx chilensis 



(rot. soc. edin. trans., vol. XLVIII., 475.) 



