4 DISCOVERY REPORTS 



large number of new species, or (ii) ' lumping ' them all into one species with a very flexible definition. 

 This problem occurs very markedly in the genera Boreomysis, Pseudomma and Euchaetomera. I have 

 perhaps erred on the side of too much ' lumping ' in these genera and I think that possibly future 

 workers may find satisfactory characters which are sufficiently constant to justify the formation of 

 several new species. 



I have found little evidence of any correlation between differences in form and geographical 

 distribution for specimens captured in the same areas and even in the same hauls display the same 

 individual variation as those from completely different localities. There does appear, however, to be 

 evidence of a geographical race in a species of Boreomysis captured in the waters around South 

 Georgia. In general form, in the shape of the rostrum and in the characteristic form of the telson, the 

 specimens agree with the descriptions of B. rostrata Illig, but they are distinctly larger and the eyes 

 are nearly twice the usual size found in this species. These characters are so noticeable that the 

 animals can be picked out with the naked eye. I would have founded a new species for them, but for 

 the fact that specimens were present in near-by localities, in which the size of the eyes and the length 

 of adult animals were intermediate between those of the normal B. rostrata and the large-eyed 

 variety. I have therefore recorded them simply as ' Boreomysis rostrata with very large eyes ' and sug- 

 gested that they may represent a geographical race. 



A total of thirty-six genera and ninety-five species is represented in the collection. Of these I regard 

 two genera and twenty-eight species as new. A review of past records and, in some cases, an examina- 

 tion of material from other collections has made it necessary to change the names of one or two species, 

 but this has only been done where absolutely necessary and full explanations are given in the text. 

 In this connexion I should like to express my gratitude to Dr Waldo L. Schmitt of the Smithsonian 

 Institution, Washington, for most generously lending me some specimens of a very rare and interesting 

 mysid for comparison with some of the Discovery material and to Dr Isobel Gordon of the British 

 Museum for allowing me to examine so many of the valuable collections in her care. 



While this work was in progress I received a small supplementary collection of Mysidacea taken 

 by R.R.S. 'William Scoresby' during a survey of the Benguela Current in March 1950. Mysids 

 occurred at twelve stations and, although the actual numbers were few, ten genera were represented 

 and sixteen species, one of which is new to science. The records are included in the list of stations of 

 the ' William Scoresby ' and a short account of the collection is added as an appendix to this report. 



I should like to express my grateful thanks to Dr N. A. Mackintosh, Deputy Director of the National 

 Institute of Oceanography for allowing me to examine this valuable and interesting collection and to 

 tender my warm appreciation and thanks to Dr Helene Bargmann for her unfailing help and en- 

 couragement throughout the course of this work. 



GEAR 



Abbreviations used in the list of stations to indicate kind of gear used 



B, oblique; H, horizontal; V, vertical; BNR, Russell's bottom tow-net; BTS, small beam trawl; DC, conical 

 dredge; DL and DLH, large dredge; DS, small dredge; LH, hand lines; N4-T, N7-T, nets attached to 

 back of trawl; N50, 50 cm. tow-net; N70, 70 cm. tow-net; Nioo, 1 m. tow-net; N200, 2 m. tow-net; N450, 

 4^ m. tow-net; NC50, coarse 50 cm. tow-net; NCS-D, NCS-T, NCS-N, tow-net attached to dredge, trawl or 

 other net; NRL, large rectangular net; NRM, medium rectangular net; OTL, large otter trawl; TYF and 

 TYF70 B, young-fish trawl. 



Where the depth of termination of an oblique haul is written '(-o)' it must be understood that the net failed to 

 close at some intended intermediate depth and fished all the way to the surface. The last part of the haul from the 

 intended depth of closing to the surface would usually occupy a small fraction of the total time of fishing. 



