THE TANGANYIKA PROBLEM. 289 



of its length there is a deep excavation of the inner side, a little beyond which 

 distally stands a stout curved spine ; a double row of strong toothed spines smaller 

 than the preceding, and gradually diminishing in size, fringe the distal margin of 

 the notch ; the oblique posterior or proximal margin is fringed with feathered or 

 pectinate setre. Beyond the notch, the inner margin of the joint bears a series of 

 6-7 short spines leading up to the pointed apex of the limb. I am not aware that 

 an arrangement similar to this is found in other Atyidcz. In C. wyckii there is only 

 a very slight concavity of the inner margin of the joint, clothed with numerous 

 spines and setae. 



The first pair of perreopods (Figs. 10, \oa) do not reach to the terminal joint of 

 the third maxillipeds. The ischium and merus are short and subequal. The carpus 

 is conical in shape, rather more than one-half as broad as long, about equal in 

 length to the merus, and slightly longer than the palmar portion of the hand ; it is 

 slightly excavated distally on the inner side (Fig. io<z). The hand is long and 

 narrow, the breadth being about one-third of the length. The fingers are slender, 

 longer than the palm, spoon-shaped, but acutely pointed as seen from the side, 

 instead of truncate as in C. wyckii. The opposed margins bear series of small 

 stout spinules increasing in size towards the tip, but there is no strong terminal 

 hook as in C. wyckii. The brushes of seta borne by the fingers are very scanty 

 compared with those of C. wyckii. 



The second peneopods (Fig. 11) reach forward as far as the tip of the third 

 maxillipeds. The ischium is a little longer than the merus and about equal to the 

 carpus. The latter is cylindrical and only slightly wider distally. The hand is 

 longer than the carpus by one-third the length of the latter, and its breadth is less 

 than one-quarter of its length. The fingers are very long and slender, about twice 

 as long as the palm, sharply pointed, and with scanty terminal brushes. 



The third pair of peraeopods extend beyond the third maxillipeds when turned 

 forward, and the last pair fall short of them. The dactylus is one-third to two-fifths 

 the length of the propodus. The dactylus of the last pair ( Fig. 13a) is similar to 

 the preceding two pairs, having only a slightly larger number of spines on its inner 

 margin, the numbers being from II to 15 in the case of the third and fourth 

 perreopods, and from 16 to 19 in the last pair. In Caridina the dactylus of the last 

 perreopods is longer and bears much more numerous series of spines than do those 

 of the preceding two pairs. In a specimen of C. wyckii, for example, the dactyli of 

 the third and fourth pairs bore seven and eight spines respectively, while the 

 dactylus of the fifth pair was half as long again and had a row of 39 spines. 



In the female, the first pair of pleopods (Fig. 14) have the endopod rather 

 slender, pointed, and more than half the length of the exopod. In the male 

 (Fig. 15), the endopod is a short' ovate leaflet about one-quarter the length of the 

 exopod. In nearly all the specimens of both sexes the first pair of pleopods are 

 turned forward, with the exopod lying above and external to the bases of the 

 posterior perseopods. According to F. Midler ("Kosmos," IX. 1881, p. 121), this 

 is the position taken by these appendages in the living Atyoida, and he states that 

 they serve to protect the entrance to the branchial chamber, the fringe of marginal 

 setae acting as a sieve to exclude mud, &c. 



In the second pleopods of the male (Figs. 17, 17a), the appendix masculina is a 

 little shorter than the appendix interna, and bears a number of stout spines. 



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