THE TANGANYIKA PROBLEM. 
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in uninjured specimens measuring more than four times the length of the peduncle, 
or about one-half the length of the body. The thickened basal part is more distinct 
than in the female. I have not observed any sexual difference in the armature of 
the walking-legs or of the maxillipeds, nor in the shape of the anterior margin of 
the carapace, such as are described by Muller in Atyoida. 
The eggs carried by the females are ovoid in form, measuring about . 18 X- 27mm. 
Total length of largest specimen ( ? ), 23 mm. 
Many specimens of this form were collected in shallow water. 
Comparing the new form with the other genera of Atyidce as revised by Ortmann 
(“ Proc. Acad. Nat. Sc.”, Philad , 1894, p. 397), we find that (like all other higher 
Atyidce) it differs from Xiphocaris, Troglocaris, and A tycephyra in the absence of 
exopods from all the perceopods. It resembles Caridina and differs from Atya and 
Atyoida in the fact that the carpus of the second perceopods is not excavated 
distally. It further agrees with the majority of the species of Caridina in the 
compressed and serrated rostrum, which, however, is much longer than in any 
species except C. gracilirostris de Man. It appears to differ from all except 
C. smghalensis Ortm. and C. brevirostris Stm. in the absence of a distinct antennal 
spine on the front of the carapace, and it certainly differs from all the species of 
Caridina , and, I believe, from all the other Atyidice, in the possession of a hepatic 
spine. The differences noted above in the shape of the first maxilla, the first 
maxilliped, and especially of the second maxilla, may possibly be of generic import- 
ance, as may also the fact that the dactylus of the last perceopods does not differ 
markedly from those of the preceding pairs. 
The most striking and important character, however, is the reduction of the 
branchial system. This has not been examined (so far as I know) in Xiphocaris , 
but the closely-allied Troglocaris possesses eight gills (Claus). Atycephyra , seven 
(Boas), Atya scabra and Caridina wyckii and typus, nine ; while there is no reason 
to anticipate any very great divergence in the closely-allied Atyoida or among the 
numerous species of Caridina which have not been examined in this respect. 
Further, all the forms hitherto examined possess (with a possible exception, as 
above noted, in the case of Atyoida) a complete series of epipods on the thoracic 
appendages. In the present form there are only four gills and no epipods at all. 
While there appears to be room for a further revision of the Atyidce based on a 
more complete examination of their morphology than that recently given by 
Ortmann, it seems plain that the form now described stands sufficiently far apart 
from the other members of the family to require the creation of a new genus for its 
reception. 
PaL/Emon Moorei,* (Fig. 4. — 20). 
Description. — Rostrum (Fig. 20) horizontal, a little longer than the peduncle 
of the antennules and equal to or shorter than the antennal scale. The nearly 
straight upper edge bears 11-13 teeth, of which three are on the carapace, the fourth 
being just over or a little in front of the posterior margin of the orbit. The distal 
tooth is close to the tip. The lower margin bears 3-4 teeth, the first being above 
the end of the first joint of the antennular peduncle. The usual antennal and 
19 * 
* Caiman, “ Pro. Zoo. Soc.,” 1899. 
