248 Records of the Indian Museum. [Vol. Ill, 



The colour is greenish-black to coal-black. 

 From North Lushai, 



d. Potamon lugubre, var. plauliim. 



In comparison with the typical form of P. lugubre : — 



The carapace is not quite so broad, and is unusually flat. 



The lateral epibranchial tooth is usually more prominent, as 

 in the variety harpax. 



The front is less deflexed and the epigastric crests are more 

 oblique. 



The wings of the cervical groove are unusually broad. 



The 6th abdominal segment of the male is slightly broader. 



From Assam and the Khasi Hills. 



e. Potamon lugubre, var. falcidigitus. 



As in the three preceding varieties the carapace is not quite so 

 broad and the front is less deflexed. 



As in the variety plautum the carapace, in most individuals, is 

 uncommonly flat, and the wings of the cervical groove are un- 

 usually broad. 



As in typical lugubre, the lateral epibranchial tooth is small, 

 indistinct, or obsolescent. 



The chelipeds have the fingers remarkably broadened, so that 

 although the upper border of the dactylus is quite as strongly 

 curved as it is in typical lugubre, yet the fingers when closed are in 

 contact, or almost so, along the whole extent of their cutting 

 edge ; but the breadth of the fingers is variable. Sometimes there 

 is a row of two or three spines or large bead-like granules on the 

 proximal end of the upper surface of the dactylus. 



In all the legs the edges of the propodite are very strongly 

 serrated, and the anterior edge of the carpus is also strongly 

 serrated. 



From Cachar, Cherra Punji, Khasi Hills, Garo Hills, and Naga 

 Hills. 



3. Potamon napceum, sp. nov. 



The species differs from P. lugubre and P. masonianum (if this 

 latter is anything more than a variety of the former) in the 

 following characters, which are constant in five males and six 

 females : — 



The carapace has an oval outline, and the antero-lateral borders 

 are well defined, sHghtly raised, and regularly beaded or crenulate. 



There is no trace of a lateral epibranchial tooth, the antero- 

 lateral borders at that point being in unbroken continuity with the 

 post-orbital crests. 



The sub-orbital lobes of the carapace are quite distinctly 

 defined. 



From Ganjam in North Cachar, 4,000 feet. 



