1918.] Stanley Kemp: Decapnda of the Inle Lahe. 101 



near Fort Stedman the whole of the hody was more or less darkened 

 with green chromatophores and was sometimes almost black. A pale 

 mid-dorsal line was nsually present, and sometimes white specks could 

 he detected on the thorax, abdomen and telson. In paler individuals 

 there was a small dark spot at the base of each pleopod. The fingers 

 of the chelae were darkened, but the bunch of hairs at the tip was often 

 v.hite. Individuals from the He-Ho stream, the water of which has 

 a peculiar blackish colour owing to the large amount of fragments of 

 carbonized vegetation it contains, were rather dark but had three parallel 

 colourless bars slanting along each side of the carapace. There was a 

 pale cross-bar on each abdominal segment and a colourless mid-dorsal 

 line." 



POSTSCRIPTUM. 



Acanthopotamon, 



nom. nov. for AcantJiotelphusa Alcock nee Ortmann. 



While this paper was still in the press Caiman published an account 

 of Potamon {Potamoficmles) warreni,^ a new river crab from the Trans- 

 vaal. The affinities of this species, which are discussed by Caiman, 

 throw much light on the position of Acanthotelphusa. 



P. {Potamonautes) warreni has an extremely close affinity with the 

 common South African P. (P.) perlatuni, differing from that species 

 only in the fact that the granules of the antero-lateral margin are re- 

 placed by spiniform teeth. The species thus affords, in the subgenus 

 Potamonautes, an instance of evolution exactly parallel to that which 

 I believe to have occurred on at least two independent occasions in the 

 subgenus Potamon, viz. in P. (P.) shensiense and P. (P.) acanthicum 

 (see p. 85). 



As Caiman has remarked P. {Potamofiautes) warreni on any of the 

 current schemes of classification would be separated generically or sub- 

 generically from P. (P.) perlatuni. Were it not for the proofs of its 

 affinity that Caiman has brought forward, it is almost certain that it 

 would have been referred to Acanthotelphusa, for it closely resembles 

 P. {Acanthotelphusa) niloticum in the character of the antero-lateral 

 margin. 



There is, as Caiman has hinted, reason for the belief that P. nilo- 

 ticu7n has originated, in much the same way as P. warreni, from some 

 East African species with normally constituted antero-lateral border. 

 But, however this may be, it is clear that its affinities are not with the 

 well-defined group of Asiatic species to which Alcock has applied the 

 name Acanthotelphusa. Since P. niloticum is the type of the latter 

 subgenus, it is evident that a new name is necessary for the Asiatic 

 forms. I suggest Acanthopotamon, distinguished from Potamon s.s. 

 by two characters, — the antero-lateral borders of the carapace are cut 

 into three or four large teeth, ^ and (ii) the upper border of the merus of 

 the chelipedes bears a sub-terminal spine. 



1 Caiman, Ann. Mag. Nat. Hist. (•!), T, p. 2,!4 (1918). 

 ^ Exclusive of the external orbital tooth. 



