i 4 o DISCOVERY REPORTS 



The specimens in the Discovery collection were captured in much shallower water than has hitherto 

 been recorded for the species, the deepest being at station 282 where it was found in a haul from 300 m. 

 to the surface. At station 290 it was taken at dawn in a haul from only 100 m. During the Benguela 

 Current Survey an adult female was taken in the morning in a haul of only 50 m. to the surface. 

 It is significant that nearly all the specimens were taken at night or very early dawn and it may well 

 be that these animals, in common with so many other mysids, frequent deeper waters by day and 

 carry out vertical upward migrations during the hours of darkness. 



The Discovery records do not add to its known geographical range. 



Arachnomysis megalops Zimmer, 19 14 



1914 Arachnomysis megalops Zimmer, p. 401, pi. 25, figs. 35. 

 1930 Arachnomysis megalops, Illig, p. 470. 



Occurrence : 



St. 252. 20. vi. 27 (night). Midway between Cape Town and Gough I., 135 m., 2 SS, 8-5 mm. 



St. 267. 23. vii. 27 (night). Off Walvis Bay, South Africa, 55o~45o(-o) m., 4 £<$, not adult; 3 $$ with large empty 



brood pouches, largest 8 mm., 4 small juv. 

 St. 268. 25. vii. 27 (night). West of Cape Frio, i5o-ioo(-o) m., 1 imm. $, 7-5 mm., 2 small juv. 

 St. 282. 12. viii. 27 (night). Gulf of Guinea, 30o(-o) m., 1 ovig. $, 7-8 mm. 

 St. 674. 25. iv. 31 (night). West of Tristan da Cunha, 280-0 m., 2 $?, 8-9-5 mm. 



St. 692. 9. v. 31 (night). Mid-Atlantic just north of equator, 350-0 m., 1 <$, 5 mm., 1 $, 4-5 mm., both juv. 

 St. 694. 10. v. 31 (night). Mid-Atlantic, south-south-west of Cape Verde Is., 210-0 m., 1 $, with very small brood 



pouch, 6-8 mm. 

 St. 697. 12. v. 31 (night). South-west of Cape Verde Is., 460-0 m., 1 $, 6-5 mm. 

 St. 699. 14. v. 31 (night). West of Cape Verde Is., 370-0 m., 1 $, 6-4 mm. 

 St. 704. 19. x. 31 (night). South of Cape Verde Is., 231-0 m., 1 juv. ?. 

 St. 706. 21. x. 31 (night). North-east of Pernambuco, 354-0 m., 1 juv. $. 



Remarks. This species can be distinguished from A. leuckartii Chun by the large balloon-like 

 eyes, which are almost as wide as they are long, and by the larger number of facets in the cornea. 

 In A. leuckartii there are from ten to fourteen facets across the largest diameter, but in this species 

 there are from eighteen to twenty-five. Zimmer figured the anterior end of his type specimen and 

 showed only four spinous processes on the anterior margin of the carapace, arranged two on either 

 side of the median line. I have not found this arrangement in any of the Discovery specimens. 

 Although the length of the spines may vary, there is always one in the median line and at least two 

 on each side of it. However, in all other respects these specimens agree so closely with the published 

 descriptions of A. megalops, that I have no hesitation in referring them to this species. 



Distribution. Zimmer's types were taken in vertical hauls from 3000-0 m. in the Gulf of Guinea 

 and west of St Paul de Loanda. Illig (1930) recorded three females from vertical hauls from 3000- 

 2000-0 m. one off the south-west of Sierra Leone and two from the Gulf of Guinea. The Discovery 

 material proves it to be widely distributed in the South Atlantic. All previous records were from 

 vertical hauls ranging through a considerable column of water, so that it was not possible to say at 

 which level the animals were actually living. It is now evident from the captures made by ' Discovery ' 

 and ' Discovery II ' that they are not confined to the deeper levels. Eight of the nine hauls in which 

 the species occurred were taken obliquely from 354-200 m. to the surface; the net failed to close at one 

 station, 267, at a depth of 500 m. All the hauls were taken at night and it may be possible that this 

 species, as well as A. leuckartii, carries out upward migrations during hours of darkness and may be 

 found in deeper water during the day. 



