THE TANGANYIKA PROBLEM. 291 



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 .i8x.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 Atyida as revised by Ortmann 

 ("Proc. Acad. Nat. Sc", Philad , 1894, p. 397), we find that (like all other higher 

 Atyida?) it differs from Xiphocaris, Troglocaris, and Atyaphyra in the absence of 

 exopods from all the peroeopods. It resembles Caridiiia and differs from Atya and 

 Atyoida in the fact that the carpus of the second peneopods is not excavated 

 distally. It further agrees with the majority of the species of Caridiiia 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. singhalensis 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 

 Caridiiia, and, I believe, from all the other Atyidia, 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 perax>pods 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). Atycepkyra, seven 

 (Boas), Atya scabra and Caridiiia 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 Atyidne 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. 



Fal.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 n-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 



* Caiman, " Pro. Zoo. Soc," \\ 



19* 



