SYSTEMATIC REPORT 71 



species and the descriptions of B. rostrata was in the length of the rostral plate. Since the type of 

 rostrata was a female, he suggested that the difference shown by Hansen's specimen was a sexual one 

 and that the two species should be united. Although I have found no specimen in the Discovery 

 collection with the rostrum quite so short or its margins quite so convex as shown in Hansen's figure 

 (1910, p. 11, fig. 4a) for B. inermis, I have found so much variation in this character that I agree 

 with Tattersall's suggestion that the two species are synonymous. 



I doubtfully refer three specimens from station 492 to rostrata. In them the rostrum is unusually 

 long, extending beyond the anterior margin of the eyes, the ocular papilla is unusually large and the 

 apex of the antennal scale is considerably shorter than the spine terminating the naked portion of the 

 outer margin. The dilatation at the base of the cleft of the telson is present, but is not very clearly 

 marked. None of the specimens is adult and the variations may be due to their immaturity. 



Distribution. Illig's females were taken at three stations in the Atlantic — off Bouvet Island, off 

 Cape Town and west of Angra Pequena — and at one in the Indian Ocean, N.E. of New Amsterdam. 

 Hansen's B. inermis, which I regard as synonymous with B. rostrata, was taken in the waters of the 

 Dutch East Indies. W. M. Tattersall (1951, p. 56) recorded the species from Alaska and Japanese 

 waters. Of the thirty-eight stations at which it was taken by 'Discovery', 'Discovery II' and 

 'William Scoresby', thirty-two are situated in the South Atlantic between 25 S. and 55 S., three 

 are in the Strait of Magellan and one in the Pacific to the east of New Zealand. Most of the hauls in 

 which it was taken were oblique from varying depths to the surface, but captures in closing nets prove 

 that it is mesoplanktonic with a considerable vertical range between 300 m. and 1300 m. 



I have recently, through the courtesy of Dr P. G. Law, Director of the Antarctic Division of the 

 Department of External Affairs, Australian National Antarctic Research Expedition, had an oppor- 

 tunity of examining some mysids collected in plankton off Heard Island by Mr E. H. M. Ealey. 

 There were six specimens in all, only one of which was adult, and, although in the smallest specimens 

 the rostrum is unusually long, I have no hesitation in referring them to B. rostrata. The single adult 

 is a male measuring 19 mm. and is in perfect condition. It is interesting that these specimens occurred 

 in plankton taken at or very near to the surface and thus the record extends its known vertical range 

 into shallower depths than hitherto known. 



Boreomysis rostrata var. Illig 

 Variety with unusually large eyes and small ocular papilla. 

 Occurrence : 



St. 42. 1. iv. 26 (day). Off Cumberland Bay, South Georgia, 120-204 m., 1 adult 2, 20 mm. 



St. 129. 19. xii. 26 (dusk to dark). Off South Georgia, 950-750 m., 1 adult 2, 24 mm. 



St. 146. 8. i. 27 (day). Off South Georgia, 728 m., 4 adult S3, 20-24 mm., 2 adult 2$, 21-6 mm. 



St. WS 29. 19. xii. 26 (day). Off South Georgia, 600-500 m., 2 small juv. 



St. WS 330. 27. xii. 28 (day). Off South Georgia, 900-760 m., 1 adult 3, 27 mm. 



Remarks. The specimens from the five stations given above agree closely with B. rostrata except 

 in the unusually large size of the eyes and the small ocular papilla. The eyes are so conspicuous, nearly 

 twice the size of those in other specimens which I have referred to rostrata, that the animals can be 

 recognized at once with the naked eye. The cornea is globular and is considerably wider than the 

 eyestalk; in all the specimens the pigment is a pale golden yellow. The papilla is unusually small and 

 insignificant and may easily be overlooked. Nevertheless, I do not feel that there is sufficient justifica- 

 tion for the foundation of a new species, especially as among the many specimens which I have 

 already referred to B. rostrata, there is a great deal of variation in the relative size of the eyes. 



