123 



length. Abdomen of adult female comparatively narrow, the length of the 'Jth 

 segment being equal to its proximal breadth. 



Antennal flagellum short. 



The edge of the epistome is deeply trilobed (as is common in Potamonidw), 

 but the outer lobes are everted so that the excurrent branchial opening is sub- 

 tubular. 



Mandibular palps as described in the diagnosis of the genus. 



The exopodites of all the maxillipeds have a strong, plumose flagellum. 

 In the external maxillipeds the exopodite is longer than the ischium, the ischium 

 is longitudinally grooved, and the merus is subquadrangular and broader than 

 long ; these appendages do not shut close against the epistome, so that the 

 channelled plate of the endopodite of the 1st maxillipeds is more exposed than 

 it is in most other Potamonida^. 



Chelipeds markedly unequal in both sexes, but most so in the adult male. 

 All three borders of the merus, the inner border of the carpus, and the upper 

 and lower borders of the palm are usually crenate or crenulate. The surface 

 of the merus is faintly rugulose ; that of the carpus is nearly smooth to the 

 naked eye, except for pitting ; that of the hand and fingers is coarsely pitted. 

 Inner angle of carpus spiniform. In the smaller cheliped the dactylus is much 

 longer than the palm ; the fingers are broad, and gape little, or not at all, at 

 base ; the teeth of the proximal half are laciniate, but none of them is much 

 enlarged, and the teeth of the distal half are small, translucent, incisor-like, and 

 very close-set and regular. In the larger cheliped also the dactylus is much 

 longer than the palm ; the fingers are compressed, and are very broad and 

 strong, and gape at base when closed ; the teeth of the proximal half are 

 laciniate and about two of them are very much enlarged, and the teeth of the 

 distal half are small, translucent, incisor-like, and are very close and regularly 

 set in a straight row. 



Legs stout, about as long as the smaller cheliped ; dactyli slender, and a 

 good deal longer than the propodites ; longer propodites hardly twice as long 

 as broad. 



In a large male the carapace is lA inch long, 2 inches broad, and 5ths inch 

 deep. 



6431 



3 

 6434 

 3 ■ 



5484 



10 ■ 



5503 



10 ■ 



