LEPTOSTRACA, SCHIZOPODA AND STOMATOPODA. 159 



larval forms is not desirable. They are, however, described and figured in the hope 

 that they may be recognised in future collections, and their life-history more fully 

 traced. 



In the preparation of this paper I have been kindly aided by Dr. NOBILI, of Turin, 

 and Professor PFEFFER, of Hamburg, with information on various species, and to these 

 gentlemen I desire to express my grateful thanks. I am especially indebted to 

 Dr. W. T. CALMAN for his kindness and help while at the British Museum, and for 

 very valuable assistance with the literature of the subject. 



I. LEPTOSTBACA. 



FAMILY : NEBALIID^E. 

 Nebalia bipes (FABRICIUS). 



Localities : 



Cheval Paar, February, 1902, 5 to 8 fathoms. Five. 



Washings from pearl oysters, Ceylon. Thirteen. 



Periya Paar, February 5, 1902, tow-net at night, surface. Few. 



The specimens of Nebalia obtained by Professor HERDMAN in Ceylon may all, I 

 think, with certainty be referred to the type species, though differing from northern 

 examples of that species in one or two minor points. They do not fall into any of the 

 numerous varieties of N. bipes recently indicated by THIELE (1904), but I do not 

 propose to designate them by a separate varietal name, because the differences are too 

 slight to deserve such an honour. Insignificant as these differences are, they serve to 

 bring still closer together the two supposedly distinct species of this genus, N. bipes 

 and N. longicornis. The characters which serve to distinguish the two latter species 

 from each other have recently been defined by THIELE (1904). Briefly, N. bipes may 

 be distinguished from N. longicornis (1) by the size of the rostrum, which in the 

 former is much longer proportionately to the breadth than in the latter ; taking the 

 breadth of the rostrum as unity, its length in N. bipes is 2*62, and in N. longicornis 

 175 ;* (2) by the armature of the fourth joint of the peduncle of the first antenna. 

 This joint in N. bipes is armed on its outer edge with at least three (sometimes as 

 many as eight, cf. N. bipcs, var. valida) spines and five or six setae, whereas in 

 N. longicornis there is only one spine and seven or eight setse. 



In N. bipes from Ceylon the rostrum is in all the specimens about two and a third 

 times as long as broad, and shaped on the whole as in THIELE'S fig. 70. The fourth 

 joint of the peduncle of the first antenna bears on its outer edge two spines (without 

 exception in all of the eighteen specimens) and four or five setae. The characters, 

 therefore, of Ceylon N. bipes are exactly intermediate between those of N. bipes 

 typica and N. longicornis. 



The specific differences between the two latter species as given by THIELE are very 



* These figures are taken from THIELE'S drawings, 1904, plate iv., figs. 66 and 70. 



