214 DISCOVERY REPORTS 



The earlier larval stages of E. vallentini are not known; those from the second 

 Calyptopis upwards are described later in this paper. 



Distribution. The stations at which E. vallentini was taken are shown in Figs. 13 

 and 14. It occurs throughout the sub- Antarctic Zone except for a narrow belt of the 

 warmest water to the north. The highest surface temperature of any of the stations at 

 which it was taken was 14-2° C, at the station south-west of the Cape on March i, i.e. 

 in summer. The stations at which it occurred in the Indian Ocean, Australian, and 

 Pacific Ocean sectors were made in winter, and the surface temperature at the northern- 

 most of them was lower, usually about 8° C. 



It was found a little way south of the Antarctic convergence in winter only. The flow 

 of Antarctic surface water to the north, strongest in summer when snow and ice are 

 melting in the south, is considerably reduced in winter when new ice is being formed 

 near the Antarctic coasts. Our observations near the convergence in winter suggest that 

 the slowing up of the current leads to a southern movement of sub-Antarctic water at 

 the surface; north of the convergence we found purely sub-Antarctic water, but the 

 Antarctic water south of it was mixed with sub-Antarctic water. In this way E. vallentini 

 becomes carried into the Antarctic Zone. The numbers taken there were small compared 

 with those from the nearest sub-Antarctic stations. The lowest surface temperature at 

 which the species occurred was 0-74° C. at the southernmost station at which it was 

 found on the line south-east of New Zealand in early September ; there was only one 

 specimen. 



Euphausia frigida, Hansen (Figs. 10, 11, 15 and 30 c) 



E. frigida, Hansen, 191 1, p. 27, fig. 9; 1913, p. 30, pi. iii, figs. \a and l\ pi. iv, figs, i a-d\ 

 Zimmer, 1914, p. 427; Tattersall, 1924, p. 20; Rustad, 1930, pp. 33, 43, 46-54, figs. 27-34; 

 Ruud, 1932, pp. 52-4; Rustad, 1934, pp. 13-18, i^et seqq.\ Mackintosh, 1934, p. j6 etseqq.; 

 Hardy and Gunther, 1935, many references. 



Euphausia sp., Tattersall, 1908, p. 14. 



E. splendens, Caiman, 1901, p. 23. 



E. crystallorophias (part), Illig, 1930, p. 500, fig. 182. 



Not E. frigida, Illig, 1930, p. 498. 



Description. The front margins of the carapace are faintly convex, the rostrum is 

 very short and triangular (Fig. 15a). 



A small triangular or rounded lobe projects forwards from the inner distal corner of 

 the first segment of the antennular peduncle ; it is difficult to see from the side. The 

 third segment has a strong dorsal keel with, as seen from the side, straight upper and 

 distal margins which meet nearly at a right-angle (Fig. 15 b). 



The abdominal segments have no dorsal spines. 



The male copulatory organ is very like that of E. vallentini and E. hicefis, but there are 

 differences which make it easy to distinguish it (Fig. 30 c). It differs from that of E. 

 lucens and resembles that of E. vallentijii in that the proximal process is longer than the 

 terminal; it resembles both species in that the proximal process carries a blade-like 

 secondary process or spine and in that it has two membranous expansions distally which 



