SYSTEMATIC REPORT 89 



Genus Anchialina Norman and Scott, 1906 



1861 Anchialus Kroyer, pp. 53, 71. 



1906 Anchialina Norman and Scott, p. 24. 



Anchialina typica (Kroyer), 1861 

 „ , • , • -,, ■■ (Fie. 15A-M) 



1861 Anchialus typicus Kroyer, p. 53, ngs. v ° J 



1910 Anchialina typica Hansen, p. 52, figs. 



1912 Anchialina typica, Hansen, p. 196. 



1951 Anchialina typica, W. M. Tattersall, p. 100. 



Occurrence : 



St. 704. 19. x. 31 (night). Mid- Atlantic just north of the equator, 231-0 m., 1 imm. <$, 4-4 mm. 

 St. WS 1000 (Benguela Current Survey). 13. iii. 50 (night). West of Orange River estuary. Three hauls: (i) 50-0 m., 

 5 small juv., 3-3-4 mm.; (ii) 100-50 m., 4 small juv., largest 3 mm.; (iii) 150-100 m., 1 adult <?, 7-2 mm. 



Remarks. The adult male from station WS 1000 and the smaller male from station 704 conform 

 very closely to the published descriptions and figures of A. typica. The small specimens from hauls (i) 

 and (ii) at station WS 1000 show certain differences which I attribute to their immaturity. In them 

 the rostral plate is hollowed from above, but its anterior end is produced between the eyes into an 

 evenly rounded rostrum (Fig. 15G). Hansen (1910, p. 52) explained that in A. typica the apparently 

 truncate anterior margin of the carapace with its distinct median emargination is in fact only the pro- 

 file of the downwardly bent rostrum. The rostral plate is hollowed from above and its anterior tip 

 is bent sharply down between the eyes, but if one raises it with a needle the anterior margin can be 

 seen to be shaped exactly as in the juvenile specimen which I have figured (Fig. 15G). 



The spines arming the lateral margins of the telson and the outer margin of the exopod of the uropod 

 in the immature specimens are few in number and are confined to the distal portion only of these 

 margins. This condition is usual in many species of mysids and is a common phenomenon in young 

 animals which are not fully grown (Fig. 15M). 



All the specimens taken at station WS 1000 are markedly hispid on the peduncles of the antennae, 

 on the eyestalks, on the pleopods of the males and, more sparsely, on the anterior portion of the 

 carapace and on some of the proximal segments of the thoracic appendages. The specimen from 

 station 704 shows only an indication of this character and I can find no mention of it in earlier descrip- 

 tions of the species. Neither does it appear in specimens, which I have seen, from Hawaii and the 

 Great Barrier Reef. The only other difference which the Discovery adult male shows is that the modi- 

 fied setae arming the distal end of the exopod of the third pleopod are curved and not straight as 

 figured by Hansen (1910, pi. vii, figs, zh and 2/). (Fig. 15 E, F.) 



On account, however, of their very close conformity in all other respects with the descriptions of 

 A. typica I have no hesitation in referring them to this species. 



Distribution. A. typica has been recorded on numerous occasions from the warmer waters of the 

 world — the East Indies, Philippines, Great Barrier Reef, Hawaii, the West Indies and from the 

 tropical regions of the Atlantic, from the coast of America to mid-Atlantic. The Discovery records 

 extend its known geographical range to the eastern waters of the Atlantic. W. M. Tattersall (1951, 

 p. 102) gave a very full account of the geographical distribution of this species and drew attention to 

 the fact that, where large numbers were taken together in night tow-nettings with the use of electric 

 light, the males far outnumbered the females. In some cases they formed 90% of the catch and in 

 others all the specimens were males. It is significant that all the Discovery captures were made at 

 night and that most of the specimens taken were males. 



