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Show 1899.] CRUSTACEANS EROM LAKE TANGANYIKA. 705 upper edge, three (rarely two) of which are behind the orbit. The teeth become more widely spaced distally, and the last one is generally separated by rather less than half the length of the rostrum from the simple, sharply pointed tip. The lower margin of the rostrum bears from 10-20 teeth, which extend quite to the tip. Below the orbit the anterior margin of the carapace is produced into a triangular tooth, but there is no " antennal" spine such as is present in most species of Caridina, e.g. in G. wyckii (Pl.XXXIX. fig. 3.). A little way back on the side of the carapace, and below the level of the sub-orbital tooth, there is a well-marked " hepatic " spine. The lower anterior corner of the carapace is evenly rounded, and there is no pterygostomial spine. The peduncle of the antennules (Pl. X X X I X . fig. 4) falls short of the distal tooth on the outer margin of the antennal scale. The first joint is about equal in length to the two succeeding joints together. The basal spine is small and slender, its tip falling short of the distal end of the joint by { the length of the joint. The short spine on the distal end of the first joint reaches to about \ the length of the succeeding joint. The ocular peduncle is rather shorter than the first joint of the peduncle of the antennule. The mandibles (Pl. X X X I X . fig. 5) are somewhat dissimilar on the two sides. The cutting-edge is separated from the molar process by a shallow emargination, within which are set two stout setae (in G. wyckii there is a row of about ten), followed at a little distance by a thick brush of finer setae just in front of the molar process. The first maxillae (Pl. X X X I X . fig. 6) differ from those of Caridina, and such allied genera as Atya and Atyaephyra, in the smaller size of the two inner lobes, the inner edges of which are much shorter, while the lobe which in these genera represents the exopod is here absent. The second maxillae (Pl. X X X I X . fig. 7) also depart somewhat from the type characteristic of the Atyidce. In the other members of the family the middle lobe of the endognath (the proximal division of the lacinia externa in Boas's nomenclature) is very much expanded, overlapping both the other lobes and presenting a very long, straight, inner edge. In the present form this lobe is much smaller, its inner edge being hardly longer than that of the distal lobe, which it does not overlap. The proximal lobe, as in the other Atyidce, is large and is overlapped for a short distance by the middle lobe. The scaphognathite is truncated anteriorly and produced to a point posteriorly, where it bears, as usual in this family, a tuft of very long slender setae, hooked at the tip but not presenting the curious swelling and tooth near the base which characterize these setae in C. wyckii. In the first maxilliped (Pl. X X X I X . fig. 8) the exopod tapers gradually from the base with hardly an indication of the external lobe (marked a by Boas) present in Caridina as in most Eukyphoia. The epipod, rudimentary in Caridina, seems to be quite absent. The third maxillipeds (Pl. X X X I X . fig. 9) extend forward as |
