224 Memoirs of the Indian Museum. [Vol. V, 



occurs abundantly in fresli and brackish water and is evidently able to tolerate great 

 changes in salinity. 



Lucifer hanseni, Nobih. 



1905. Lucifer hanseni, Nobili, Bull. Miis. iVHist. nat., Paris, p. 394. 



1906. Lucifer hanseni, Nobili, Ann. Sci. nat., Zool., (9), IV, p. 25, pi. ii, fig. i, and text-figs. 36, 



p. 27. 



The specimens from the Chilka Lake, along with others obtained by the 'Inves- 

 tigator' in various parts of the Bay of Bengal, undoubtedly belong to this species. 

 L. hanseni, as Nobili has remarked, is closely allied to Dana's L. reynaudi ( = 1. 

 typus of Nobili and other authors); but his table for their separation is in .some res- 

 pects misleading. Judging from the material in the Indian Museum the principal 

 distinctions between the two forms are as follows : — 



L. hanseni, Nobili. 



'Neck' shorter ; in female from 2i to 2J times, 

 in male twice or less than twice the length of 

 remainder of carapace. 



Eyes not quite reaching distal end of basal anten- 

 nular segment. 



Abdominal segments with a spine above base of 

 pleopods in very large males only. 



Sixth abdonrinal somite from 2 to 2J times as 

 long as deep, without or with only a very small 

 postero dorsal spine (text-figs, ^ya, b). 



Anterior spine on ventral margin of si.^th abdom- 

 inal somite of male situated much nearer to 

 posterior spine than to anterior margin of seg- 

 ment; no spiuules behind posterior spine. The 

 same margin in female unarmed, rarely with a 

 pair of fine spiuules placeil posteriori}- (text- 

 figs. 57" > ^)- 



Spine at distal end of outer uropod not nearly 

 reaching to distal end of segment (text-figs 37 

 c, d). 



L. reynaudi (Milne-Edwards) Dana. 

 ( = L. typus, Bate, Ortmann, Nobili.) 



' Neck' longer; in female from 2| to 2| times, in 

 male about 2j times the length of remainder of 

 carapace. 



Eyes reaching to or beyond distal end of basal 

 antennular segment. 



Abdominal segments with a strong spine above 

 base of pleopods in both sexes. 



Sixth abdominal segment from 2| to 3 times as 

 long as deep, with a more conspicuous postero- 

 dorsal spine (text-figs. 38a, b). 



Anterior spine on ventral margin of sixth abdom- 

 inal somite of male situated altno.st midway 

 between posterior spine and anterior margin of 

 segment ; a pair of fine spinules frequently pres- 

 ent behind posterior spine. The same margin 

 in female always provided with a pair of fine 

 spinules placed posteriorly (text-figs. 38^, b). 



Spine at distal end of outer uropod reaching 

 almost to, or in young males beyond, distal 



1 end of segment (text-figs. 38c, d). 



In addition L. hanseni is decidedly stouter in build and the antennal scale is 

 broader (about 9 times as long as broad in L. hanseni as compared with 11 times as 

 long as broad in L. reynaudi). The ' phymocerite ' at the base of the antennae is 

 certainly present in some specimens of L. hanseni; but in others it appears to be 

 missing. 



In practice the most useful of the characters noted above is the difference in the 

 form of the outer uropod. The po.sition of the spine on the external margin is a 

 valuable aid to identification in the species of Lucifer; in L. acestra it is different 

 from both the species mentioned above, extending in both adults and young far 

 beyond the apex of the lamella. 



