2 88 
THE TANGANYIKA PROBLEM. 
the antennal scale by J to nearly 4 its length. There are from 12-15 teeth on its 
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 rostium 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 C. wyckii (Fig. 3). A little way back on the side of the cara- 
pace, 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 (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 J the length of the 
succeeding joint. The ocular peduncle is rather shorter than the first joint of the 
peduncle of the attennule. 
The mandibles (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 sette (in C. wyckii there is a row of about 10), followed at a little 
distance by a thick brush of finer setae just in front of the molar process. 
The first maxillae ( 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, w hile the lobe w hich in these genera represents the exopod 
is here absent. 
The second maxillae (Fig. 7) also depart somewhat from the type characteristic of 
the AtyicUe. 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 Atyida , is large and is overlapped for a short distance by the 
middle lobe. The scaphognathite is truncated anteriorly and produced to a point 
posteriorly, w'here it bears, as usual in this family, a tuft of very long, slender seta;, 
hooked at the tip but not presenting the curious swelling and tooth near the base 
which characterise these seta; in C. wyckii. 
In the first maxilliped (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 Eukyphota. The spipod, rudimentary in Caridina , seems to be quite 
absent. 
The third maxillipeds (Fig. 9) extend forward as far as the end of the first joint 
of the peduncle of the antennules. There is on the outer surface of the coxal joint a 
conical curved papilla similar to, but smaller than, the papilla to which the epipod 
of this appendage, here absent, is attached in C. wyckii. The exopod exceeds in 
length the joint from which it springs. The terminal joint is shorter than the 
penultimate joint, and presents a remarkable structure (Fig. 9 a). About the middle 
