18 R. NORRIS WOLPENDEN. 



Giesbrecht's species E. austrina, though I have found it in the ' Gauss ' collections. 

 E. antarctica appears in many stages, extensive captures consisted wholly of 

 immature specimens, but there are many adult examples. Many males appear amongst 

 these, and while the females are very distinctively different, I am not able to discrimin- 

 ate between those males, as to which definitely belong to antarctica, and others 

 which might belong to similis. Both species are very closely allied, and differ 

 very considerably from the large species of the northern cold seas, viz., norwegica, 

 glacialis and barbata. 



EUCHAETA ANTARCTICA. 



(Plate IV., figs. 5, 6.) 

 EucJueta antarctica, Giesbrecht, 'Belgica' Report, p. 21. 



This is one of the most abundant copepods in the ' Discovery ' collection, appearing 

 in all stages of growth, and in some samples almost to the exclusion of other species. 



Size of adult examples 7 ' 6 mm.-8 mm. Head evenly rounded, without frontal 

 prominence and with short rostrum directed forwards. Last thoracic segment with 

 rounded margins, produced forwards and with a bunch of hairs on each side. The 

 abdominal segments have the postero-distal margins armed with rather strong bluntly 

 conical and striated teeth, and the two middle segments have on the ventral side 

 bunches of long hairs. The furca and bristles are the same as in E. similis. The 

 genital protuberance occupies the lower half of the segment, its upper margin is not 

 deeply concave like similis, but the whole swelling is directed downwards, and its upper 

 margin is slightly convex. Above the genital swelling is a secondary prominence, 

 which in the ventral aspect is seen to consist of two valve-like chitin thickenings. The 

 lower part of the protuberance has two lateral lobes, the upper are small, and above this 

 a prominent horn directed straight forwards and never absent in adult specimens of 

 E. antarctica, making it quite characteristic of the species. 



In the ventral aspect the appearance is quite different from that of similis. The 

 genital opening is oval, almost round, with lateral cushions, and above the upper edge 

 of the genital opening guarded by a chitin ridge, is the horn. 



The whole swelling is quite symmetrical, rather conical, and occupies quite the 

 lower part of the segment. 



The first pair of feet have the outer margin very concave above and very convex 

 below, with a bunch of hairs on the Re 1 , and a long seta. The seta of Re 2 is also 

 very long and thin. The Re 3 is only half the length of the coalesced Re 1 and 2. 



In the second pair the Re 1 has a very short Se, that of Re 2 is very long and 

 more than twice as long as the Se 1 of Re 3. 



In Re 3, the Se 1 does not reach the origin of Se 2, the Se 2 does not quite reach 

 the end of the segment, and is three times as long as Se 3 and twice as long as Se 1. 

 The Sf 1 and 2 are very greatly curved and almost sickle-shaped. 



