Cumacea: 9. Leuconidae, 1. Leucon 63 



1. Gen. Leucon Kroyer 



1846 Leucon (part.), Kroyer in: Naturh. Tidsskr., ser. 2 v.2\i p. 208 j 1855 L., 

 W. Liljeborg in: Ofv. Ak. Forh., 1855 u 12 p. 121 | 1865 X., G. O. Sars in: Forh. 

 Selsk. Christian., 1864 p. 176 | 1871 L., G. 0. Sars in: Svenska Ak. Handl., n. ser. 

 17.9 nr. 13 p. 38 | 1879 L., G. O. Sars in: Arch. Naturv. Kristian., vA p. 23 | 1887 L., 

 G. 0. Sars in: Rep. Voy. Challenger, v. 19 pars 55 p. 33 | 1896 Lewcowopsis, A.O.Walker 

 in: Rep. Brit. Ass., 1896 ». 66 p. 417 | 1897 L., A. O. Walker in: J. Linn. Soc. London, 

 U.26 p. 227 I 1900 Leucon, G. 0. Sars, Crust. Norway, v.2, p. 29 ] 1907 L., Caiman 

 in: Tr. zool. Soc. London, v.lSi p. 31 | 1908 L., Zimnier in: Ergeb. Tiefsee-Exp., v.% 

 p. 176 I 1909 L., Stappers in: Cellule, u 25 p. 369 (alimentary system) ] 1911 L., Stappers 

 in: Camp. arct. Orleans, Crust. Malac. p. 99 | 1912 Z., T. Stebbing in: Ann. S. Afr. Mus., 

 i;. lOv p. 156. 



Pseudorostral projection prominent, carapace with longitudinal, medio- 

 dorsal, serrate crest in female, often wanting in male. Peduncle of first 

 antenna without conspicuous geniculation, accessory flagellum usually very 

 small. Terminal joint of second antenna in female well defined. Hepato- 

 pancreatic glands with four pairs of lobes. 



20 species. 



Synopsis of species: 



( Branchial siphon monstrously extensile 1. L. siphonatus 



\ Branchial siphon not monstrously extensile — 2. 



{Pseudorostrum 9 more than half length of rest of 

 carapace 2. L. tenuirostris 

 Pseudorostrum not more than half length of rest of 

 carapace — 3. 

 J Uropods with rami subequal — 4. 

 \ Uropods with rami not subequal — 10. 

 / Dorsal crest of 9 carapace serrated throughout its 

 length — 5. 



\ Dorsal crest of 9 carapace with partial or interrupted 



I uo 



serration — Q. 



1 Pseudorostrum truncate 3. L. nasieoides 



\ Pseudorostrum acute 4. L. australis 



/ Uropods with 2iid joint of endopod more than half as 



long as the 1st 5. L. fulvus 



6 • 



j Uropods with 2iid joint of endopod not more than 



' half as long as the l^t — 7. 



j Medio-dorsal serrations reaching end of carapace after 



7 I an interval — 8. 



I Medio-dorsal serrations not reaching end of carapace — 9. 



{Antenna 1, accessory flagellum much shorter than 1 st 

 joint of principal 6. L. nasica 

 Antenna 1, accessory flagellum as long as 1st joint 

 of principal 7. L. antaretieus 



{Uropods with 2ii<i joint of endopod half as long as 1st 8. L. nathorsti 

 Uropods with 2iid joint of endopod much less than 

 half as long as 1 st . . . 9. L. septemdentatus 



( Uropods with exopod shorter than endopod — 11. 

 \ Uropods with exopod longer than endopod — 14. 



1 Antenna 1 with accessory flagellum shorter than 1st 

 joint of principal 10. L. mediterraneus 

 Antenna 1 with accessory flagellum not shorter than 

 1st joint of principal — 12. 



