PRAWNS FROM LAKE TANGANYIKA. 435 



a didactylous hand. They are, however, still com iiaratjvely short, 

 and do not exhibit the full number of joints, the ischial joint 

 being not yet separated from the nieial one. The hand is also 

 imperfect in so fai- as none of the iingei'S is as yet mobile, Both 

 lingers are clothed at the obtuse extremity with a few veiy slender 

 bristles, and similar bristles are also attached inside the other 

 joints. The natatory exopodite is about the length of the endo^ 

 podite, and of exactly the same structure as in the maxillipeds. 



The three succeeding pairs of legs, the pereAopoda (figs. 13 & 14), 

 are a little longer than the chelipeds, and have the endopodite of 

 cylindric form and more or less curved, being composed of four 

 well-defined joints. The last joint, or dactylns, is conical in 

 form and cairies on the tip a slender spine accompanied by a few 

 bristles. Similar bristles, partly of considerable length, are also 

 attached to the inner side of the other joints. The two anterior 

 pairs (tig, 13) carry well-developed natatory exopodjtes of the same 

 structure as those on the chelipeds, whereas the last pair (fig, 14) 

 do not exhibit any trace of such appendages. 



'ihe pleopoda (figs. 15tfc 16), as in the adult animal, consist each 

 of a somewdiat flattened, oblong quadrangular basal part and two 

 terminal, lanceolate lauiella?, apparently answering to the ejido- 

 podite and exopodite. These lamellae, however, still only exhibit 

 very slight traces of marginal setae in process of formation. On 

 the 1st pair (fig. 15), as in the adult animal, the inner lamella is 

 rudimentary; on the other pairs (fig. 16) it is well develo})ed, 

 though somewhat shorter thaii the outer one, and carries inside, 

 at some distance from the base, a small digitiform appendage. 



The telson (fig. 17) has the form of an oblong quadiangular 

 plate, well defined from the last caudal segment, and slightly 

 exceeding half its length. It is armed at the neai'ly ti'ansversely 

 truncated extremity with eight spines of unequal size, the two 

 outermost being much the longest and somewhat diverging, the 

 two innermost and the outermost but one on each side rather 

 small. 



The uropoda (fig, 17) have the outer plate of a shape very similar 

 to that of the antennal scale ; the inner one Is a little shorter and 

 lanceolate in form. Both plates are fringed with ciliated setae 

 and extend somewhat beyond the telsop. 



Occurrence, — The solitary specimen described above was found 

 in a sample taken at Sumbu (S.W. of lake). In the game sample 

 also occurred a few very young s|>ecimens of Limnocaridina 

 parvida Caiman, 



Young Prawn in the 1st Postlarval Stage. (PI. LX.) 



There cannot, I think, be any doubt that the spepimen described 

 below and figured on the accompanying [)late is lefeiuble to 

 the same species as the preceding larva, and accordingly is a 

 developing stage of Limnocaridina parimla Caiman. The simi- 

 larity in the general aspect is vei'V striking, and the difference in 



28* 



