SCHIZOPODA. 7 



(2) In E. superha the rostrum is shorter and blunter than in E. murrayi, and has 

 the margins less deeply concave. This, again, is clearly shown to be a sexual 

 difference in PI. I., Figs. 1 and 2. The rostrum of the male figured (Fig. 2) is shorter 

 than that of the female, but is still rather more acute than in Sars' figure of E. superba. 

 Reduction is probably not complete till a size of at least 48 mm. is attained. 



A further difference between the two sexes is brought out by the figures here 

 given, namely, the reduction in the male of the spine on the outer distal corner of the 

 basal joint of the antennular peduncle. It is not visible in dorsal view, being hidden 

 by the slightly projecting anterior margin of the joint, but it still persists as a small 

 blunt protuberance. In the female, on the contrary, it is well-developed, distinctly 

 visible in dorsal view, and acutely pointed throughout life. 



A fourth distinction shown in the figures, the absence in the female of the curved 

 setae on the dorsal surface of the basal joint of the antennules, is due to the accident 

 that in the female from which the figure was taken, these setae had become broken off. 

 They are, in reality, present, and equally developed in both sexes. 



The above detailed description proves, I think, clearly, that E. superba and 

 E. murrayi are the adult male and female, respectively, of one species which must bear 

 the name E. superba Dana. 



I also give (Plate I., Figs. 5-9), figures of the mouth organs and endopods of the 

 first two thoracic limbs, to show two characters in which E. superba differs from all 

 other Euphausia yet described. The first of these points is the narrow and elongate 

 form of the terminal joint of the mandibular palp, with its peculiar armature of four or 

 five terminal strong plumose setae. In all the other species of the genus (with the 

 exception of E. antarctica, Sars, and E. glacialis, Hodgson), the terminal joint of the 

 mandibular palp is much shorter and stouter. In the two exceptions just mentioned 

 the mandibular palp is figured by Sars and Hodgson respectively, almost exactly as 

 here given for E. superba. This fact first suggested to me that these two species were 

 only developmental stages of £. superba, a suggestion fully borne out by the evidence 

 derived from a study of the present collection. The second distinctive character of the 

 appendages is found in the great length of the setae arming the joints of the thoracic 

 limbs. They are very much longer than in any other species of the genus, and with 

 the character of the mandibular palp serve for recognition of E. superba at any stage 

 in its development. 



Euphausia superba is the giant of the genus, and the only one of Dana's original 

 four species which is now retained by Hansen (1905 (2) ), the other three having been 

 cancelled by that author as unrecognisable. 



Some Notes on the development of E. superba. 



These notes were made chiefly with a view to confirming the suspicion, aroused 

 by the similarity in mouth organs, that Euphausia antarctica and E. glacialis were 

 merely developmental stages of E. superba. The changes which accompany growth to 



E 2 



