290 



THE TANGANYIKA PROBLEM. 



The telson (Fig. 18) is about as long as the inner plates of the uropods, with 

 straight sides, tapering to the obtusely pointed tip which bears four spines, two 

 short external and two longer internal, between which latter spring three plumose 

 setae. On the dorsal surface of the telson are two pairs of spinules. In C. wyckii 

 the tip of the telson bears eight spines, and the dorsal surface three pairs of 

 spinules. 



The gills are four in number on either side, three pleurobranchs, corresponding 

 to the second, third and fourth peraeopods, and one which I believe to be a pleuro- 

 branch (though it is difficult to determine the precise point of insertion) above the 

 first peraeopod. There are no epipods on the maxillipeds or peneopods, unless we 

 regard as a rudimentary epipod the small papilla at the base of the third maxilliped 

 described above. In tabular form the arrangement is : — ■ 



The statements of various authors as to the branchial formulae of the genera 

 of Atyida are somewhat conflicting, but all agree in giving a larger number of gills 

 and a complete series of epipods as far as the fourth perieopods. 



In C. wyckii and C. typus I find the following arrangement : — 



This agrees with the formula for Atya. Claus states that Troglocaris lacks the 

 arthrobranch of the first perreopod. According to Boas, Atyaphyra desmarestii has 

 no arthrobranch on the first perreopod, and only one on the third maxilliped. 



The males are usually somewhat smaller than the females, and have as usual the 

 pleural plates of the abdomen less deep. In the female the two flagella of the 

 antennule are of about equal length, and about twice as long as the peduncle, the 

 outer flagellum being slightly thickened for about two-thirds of its length. In the 

 male both flagella are much elongated, the outer being longer than the inner, and 



