SYSTEMATIC REPORT 173 



simple unsegmented plates; in the male the first and second pairs rudimentary as in the female; 

 third pair well developed, biramous, multi-articulate; fourth pair biramous with the endopod normal, 

 multi-articulate; exopod extremely long, multi-articulate and armed distally with long modified setae; 

 fifth pair well developed, biramous and multi-articulate. Telson long and narrow with the lateral 

 margins nearly straight and armed with many small spines; apex deeply cleft, the margins of the 

 cleft armed with a regular row of closely set, very small teeth. 



Only two species have, up to the present, been referred to this genus, A. maxima (Hansen, in MS.) 

 Holt and Tattersall and A. ohlini Hansen. The genus has always been regarded as purely Antarctic, 

 but the capture of four, nearly adult specimens at station 274 off St Paul de Loanda, Angola, 

 West Africa in a latitude of only 8° 40' S. is most astonishing. I have carefully examined hauls from 

 stations between the Falkland Islands and Africa, and along the west coast of Africa, but have found 

 no trace of either of the species of this genus. Neither species has been recorded from the northern 

 hemisphere. 



The genera most closely allied to Antarctomysis are Mysis, Hemimysis and Arthromysis and, since 

 the real differences between them lie in the form of the male pleopods, it is most difficult to decide to 

 which genus female specimens should be referred. In all four genera the first and second pairs of 

 pleopods in the male are reduced to simple unsegmented plates as in the female. In all of them also 

 the third pair are biramous, but only in Antarctomysis are both rami normal and multiarticulate. In 

 Mysis and Arthromysis the exopod is normal but the endopod is unsegmented and reduced to a simple 

 plate. In Hemimysis both rami are very small, the exopod reduced to a small knob and the endopod, 

 at most, two-segmented. In all four genera the exopod of the fourth pair is extremely long and armed 

 distally with long modified setae, but in Antarctomysis alone the endopod is normal and multi- 

 articulate. In Mysis and Arthromysis the endopod is reduced to a simple unsegmented plate and in 

 Hemimysis it is very small and obscurely two-segmented. The fifth pair of pleopods is well developed 

 and normal in Hemimysis, Arthromysis and Antarctomysis, but in Mysis it is reduced to a single plate 

 which is usually unsegmented, but may be two-segmented. Antarctomysis can be distinguished from 

 Arthromysis by the absence of two long plumose setae at the base of the cleft of the telson; from 

 Hemimysis, by the form of the antennal scale. In Antarctomysis this is setose all round, but in 

 Hemimysis the outer margin is unarmed distally, with no tooth or spine marking the distal end of the 

 naked portion. In one species, however, H. serrata Bacesco (1938, p. 425), the outer margin of 

 the antennal scale is armed with spines instead of setae. 



It is fortunate that both the species of the genus Antarctomysis are abundant and gregarious in 

 habit, so that males are usually available and the form of their pleopods leaves no doubt as to the 

 genus to which specimens belong. 



Antarctomysis maxima (Hansen in MS.) (Holt and Tattersall), 1906 



19066 Alysis maxima (Hansen in MS.) Holt and Tattersall, p. n. 



1906 Antarctomysis maxima Coutiere, pp. 1-10. 



1908 Antarctomysis maxima, Hansen, p. 13, figs. 



1908 Antarctomysis maxima, Tattersall, p. 36, fig.; 1913, p. 872; 1918, p. 12; 1923, p. 301. 



1913 Antarctomysis maxima, Hansen, p. 19. 



1915a Antarctomysis maxima, Zimmer, p. 203, figs. 



1935 Antarctomysis maxima, Hardy and Gunther, p. 201, fig. 



Occurrence : 



St. MS 20. 9. iv. 25 (day). Cumberland Bay, South Georgia, 40-0 m., 1 ?, 15 mm. 

 St. MS 22. 9. iv. 25 (day). Cumberland Bay, 40-0 m., 2 $9, juv. 

 St. MS 26. 15. iv. 25 (day). Cumberland Bay, 10 m., 1 small juv. $. 



