222 DISCOVERY REPORTS 



As Caiman has pointed out (1917, p. 157, and 1927, p. 399) the classification of the 

 forms of Nebalia is, at present, very unsatisfactory. The chief characters on which 

 species are diagnosed are : the form of the rostrum, the setal armature of the fourth 

 segment of the antennule and, to a lesser degree, the form of the eye. 



If the second of these characters alone is taken into consideration all the Discovery 

 specimens belong to the species A'^. longicornis, since they all carry on the fourth anten- 

 nular segment one stout spine followed by five or six more slender spines. Also, the 

 single specimens from South Georgia and the Falkland Islands exhibit eyes with the 

 peculiar dorsal tubercle characteristic of the variety N. longicornis magellanica (Thiele, 

 1904, p. 13, and 1905, p. 66). 



Considering the rostrum, however, it is not so easy to give a satisfactory name to 

 the specimens. There seems to be some confusion as to the dimensions of the rostrum 

 which characterize the two forms N. bipes and N. longicornis. From Caiman's accounts 

 it appears that he takes a ratio of length to breadth of the rostrum of about 2 : i as being 

 characteristic of N. longicornis while he quotes 2-3 : i as being typical of N. bipes (1917, 

 p. 156). I have measured the two figures published by Thiele (1904, PI. 4, figs. 66 and 70) 

 and the ratios are, for N. longicornis 173 : i and for N. bipes 2-61 : i. 



The ratios of the Discovery specimens are: St. 45, 2-07:1; St. 51, 2-37:1; St. 90, 

 2-52:1, 2-40 : 1 , 2-40 : 1 . Thus they all fall in between Thiele's figures over a wide range. 

 It is obvious that, at least in this collection, it is useless to consider rostral measurements 

 and I have accordingly classified the specimens solely on their antennulary armature. 



LITERATURE 



Calman, W. T., 1917. Crustacea. IV. Stotnatopoda, Cumacea, Phyllocarida and Cladocera. Brit. Antarct. 



('Terra Nova') Exp., Zool. in. No. 5, pp. 137-62. 

 1927. Report on the Phyllocarida, Cumacea and Stomatopoda. Cambridge Exp. Suez Canal, Trans. 



Zool. Soc. London, Pt 3, 1927, pp. 399-401. 

 Cannon, H. G., 1927. On the Feeding Mechanism of Nebalia bipes. Trans. R. Soc. Edinburgh, lv, pp. 



355-70- 

 ■ 1928. On the Feeding Alechanism of the Fairy Shrimp, Chirocephalus diaphanus. Trans. R. Soc. 



Edinburgh, LV, pp. 807-22. 

 Cannon, H. G. and Manton, S. M., 1929. On the Feeding Mechanism of the Syncarid Crustacea. Trans. 



R. Soc. Edinburgh, LVI, pp. 175-89. 

 Claus, C, 1889. Organismus der Nebaliiden und systematische Stellung der Leptostraken. Arb. Zool. Inst. 



Univ. Wien, viii, pp. 1-149, pis. 1-15. 

 Ohlin, a., 1904. tJber eine netie bathypelagische lebende Phyllocaride. Zool. Anz. Leipzig, xxvii, pp. 59-61. 

 Thiele, Joh., 1904. Die Leptostraken. Wiss. Ergebn. D. Tiefsee-Expedition 'Valdivia', viii, pp. 1-26, 



pis. 1-4. 

 ■ 1905- Ueber die Leptostraken der Deiitschen Siidpolar-Expedition 1901-1903. D. Siidpolar-Exp., ix 



(Zool. i), pp. 61-8, pi. 2. 

 Sars, G. O., 1887. Report on the Phyllocarida collected by H.M.S. 'Challenger' during the years 1873-1876. 



Rep. Voy. 'Challenger', Zool. xix, 38 pp., 3 pis. 



