EUPHAUSIA SIMILIS 233 



taken was - 176° C. at one of the stations near the ice-edge south-east of New Zealand 

 in September. 



It occurs north of the Antarctic in the coldest water of the sub-Antarctic Zone. The 

 highest surface temperature at which it was taken was 9-05° C. at the northernmost of 

 the two stations south of the mid- Atlantic, and only two specimens were found there. 

 It is not usually found in such warm water. Two specimens were taken unusually near 

 the northern limit of the sub- Antarctic Zone to the south-east of New Zealand. The 

 salinity of the surface water showed that there was a strong movement of sub-Antarctic 

 water to the north along the 2000-m. contour line east of New Zealand, towards the 

 Chatham Islands. 



There are reasons, which I hope to give in a later paper, for believing that E. triacantha 

 breeds only in the narrower part of its range, in the sub-Antarctic, and that as it de- 

 velops it is carried into the Antarctic Zone by the southward flowing warm deep current. 



Euphausia similis, Sars (Figs. 24-26) 



E. similis, Sars, 1885, p. 79, pi. xiii, figs. 1-6; Ortmann, 1893, P- 12; Coutiere, 1906, p. 7; 

 Hansen, 1913, p. 29, pi. iv, figs. 3 a-e\ Zimmer, 1914, p. 425; Hansen, 1915, p. 80; 1916, 

 p. 642; Tattersall, 1924, p. 18; 1925, p. 7; Illig, 1930, p. 498. 



Description. The anterior part of the carapace is produced on either side to form 

 an obtuse projection behind the upper part of each eye (Fig. 24 a). The rostrum is strong 

 and sharp and reaches as far forward as, or a little farther forward than, the eyes. The 

 front part of the carapace is arched and keeled and the keel runs out along the rostrum 

 (specimens with deformed rostra are not uncommon — see below). 



A strong and conspicuous bifid lobe rises arch-like, forwards and upwards, from the 

 inner part of the distal margin of the first segment of the antennular peduncle ; the inner 

 of the two forks is the longer and it is curved outwards, the outer may point outwards 

 but it is straight (Fig. 24 a, b). The inner distal corner of the upper margin of the second 

 segment is produced into a short, blunt, tooth-like process ; it is the end of a low keel 

 which runs along the inner side of the upper surface of the segment. There is a shorter 

 and blunter projection on the outer distal corner. The third segment has a strong dorsal 

 keel which, seen from the side, appears to start about one-third of the way along the 

 segment ; its upper margin is arched, its front margin oblique. 



The hinder margin of each of the first and second abdominal somites is produced 

 mid-dorsally into a very small triangular or rounded projection which can be seen in 

 profile by pressing away the tergum of the somite behind it. The hinder margin of the 

 third somite may have a wider, rounded and less obvious projection. 



The terminal process of the male copulatory organ has a foot-like base with a strong 

 high heel (Fig. 25 a). The shaft runs straight and tapers gradually towards the end, 

 which is turned sharply forwards and inwards. On the inner and forward side just 

 before the end there is a large and blunt projection of a complicated structure ; it seems 

 to be of thin walls held out by heavy bars and struts of chitin. 



The distal part of the proximal process is bent inwards, nearly at a right angle to the 



