12 W. M. TATTERSALL. 



latter size the species has all the adult characters, except perhaps the rostrum, which 

 has the margins hardly as concave as fully adult specimens. Examples of 13 mm. 

 in length are to be met with in January, and so were presumedly larvge of the 

 preceding season, from which it would appear that the species takes at least one 

 year, and very probably longer, to reach the final adult size of 32 mm. 



EUPHAUSIA TRIACANTHA. 



(Plate IV., Figs. 1-3.) 

 Euphausia triacantha. Holt and Tattersall, 1906 (1). 



Locality of capture : Lat. 66 52' 09" S., long. 178 08' 15" E., 2030 fathoms; 

 one specimen, immature male, 23 mm. 



Carapace (Plate IV., Fig. 1), with a single lateral denticle posterior to the centre 

 of the lower margin of the carapace ; antero-lateral margins somewhat inflated over 

 the eyestalks, and then produced into a long and very acute rostrum, which extends 

 beyond the eyes and almost to the distal end of the basal joint of the antennular 

 peduncle ; a faint keel is present on the carapace behind the rostrum. 



Pleon (Plate IV., Fig. 1) with the posterior dorsal margin of the terga 

 of the third, fourth, and fifth segments produced into rather long, slender, very acute 

 and slightly curved median spines ; sixth segment rather long, nearly twice as long 

 as the fifth segment without the spine. 



Eyes somewhat damaged in the single specimen, but apparently rather small, 

 pyriform in shape. 



Antennular peduncle (Plate IV., Fig. 2) bearing on the inner distal corner of 

 the basal joint a well-developed bifid leaflet, the lappets of the leaflet of about equal 

 size ; outer corner of the basal joint rounded and adorned with numerous rather long 

 plumose setae ; a row of six curved plumose setae on the dorsal surface of the basal 

 joint ; second joint with a simple acutely spiniform lappet arising from the median 

 anterior margin ; third joint slightly narrower and shorter than the second. 



Antennal peduncle shorter than the scale, the third joint a little shorter than 



the second. 



Antennal scale reaching very slightly beyond the distal extremity of the second 

 joint of antennular peduncle, broadly " oval in shape, about three times as long as 

 broad, apex broadly and obtusely rounded, spine at the distal end of the outer margin 

 small but distinct ; spine on the outer distal corner of the basal joint long, slender 

 and smooth. 



First pleopods of the male (Plate IV., Fig. 3) obviously not fully metamorphosed, 

 since both the proximal and distal movable processes on the endopod are small 

 and simple, and the uncinus on the middle lobe is without a secondary spinule. 



Tdson with the portion between and posterior to the sub-apical spines acutely 

 produced and smooth ; sub-apical spines extending beyond the apex of the telson, 



