50 



PHYLI.OPOD CRUSTACEA 



6". simplex. The finger-notch is generally more deep and open than in the forms described 

 alxive, and the main branch of the fing'er is always Ijifnrcated for al)Out its last third. The 

 bifurcation is so constructed that from the outer side the ventral branch appears to be an 

 enlarged spine, while from the inner face, the dorsal branch gives that appearance. Both 

 branches may be smooth, or either or both may bear minute spinules. Baird had only the S 

 (if this species, and Sars says "y\ntenna€ in female simple, blade-like, bluntly rounded at the 

 tip: . . ." All 16? 9 examined by me had the 2nd antennae folded and wrinkled to a 

 greater or less degree, even the very immature specimens from Alirzapur showing it plainly 



Figure 13. — Strcplocephalns. A, left 2nd antenna of young $ S. simplex from Nundy, seen from outer side. 

 B, same, somewhat older specimen. C, left 2nd antenna of young S S. dichoiomus from Mirzapur, of about the 

 same age as 13, D, head of a very young 9 -f. simplex from Nundy, seen from in front. The Nundy specimens 

 are too young to determine the subspecies. 



This agrees with the statement of Alcock (1897) who described the species under the name of 

 BranchipHs (Strcptoceplialus) bcngalensis, though his figure is almost the precise antithesis 

 of his description. The 1st antennae of the 9 9 , and to a lesser extent of the S S , are fre- 

 quently coiled, and often hidden under the 2nd antennae. In neither sex do the 1st antennae 

 appear segmented. 



The bifurcation of the main branch of the 2nd antennae of the S appears very early. 

 A young stage is shown in Figure 13, c. (The 5". simplex from Nundy, Figure 13, a, b, d, are 

 not old enougli to place certainly as to subspecies, except to say that they are not echinus. 

 They are in all probability S. s. simplex.) 



All the forms of Streptocephahis here in discussion are quite closely related to each 

 other, but not to any other forms. If we regard the fiat, unfolded 2nd antenna of the 9 

 as primitive (it appears nearly universally throughout the genus), it is clear that the oldest 

 member of the group is that closest to the African center of distribution of the genus. No 

 Streptocephali are known to occur along the present land route between Arabia and India. 

 This may be because of inadequate collecting, or the distribution may have taken place before 

 the present arrangement of the land masses. 



