292 



Records of the Indian Museum. 



[Vol.. VIII, 



cles in the vicinity of the 



small but acute epibranchial 



tooth ; crenulate antero-late- 



ral margin sharply pinched 



off from the general surface decourcyi, sp. nov. 

 II. Post-orbital crests not sharp-edged 

 or undermined, but merged to some 

 extent in the large rugosities of the 

 anterior part of the carapace. 



a. Carapace feebly convex fore 



and aft ; crenulate antero- 

 lateral margin well defined, 

 but not strongly curved 

 inwards; a very small and 

 inconspicuous gap in the 

 margin anterior to the obso- 

 lete epibranchial tooth 



b. Carapace strongly convex fore 



and aft; crenulate antero- 

 lateral margin well defined 

 and strongly curved in- 

 wards; a deep gap in the 

 margin anterior to the large 

 blunt epibranchial tooth . . aborense, sp. nov. 



c. Carapace strongly convex fore 



and aft ; crenulate antero- 

 lateral margin obsolete, de- 

 fined merely by a few isola- 

 ted tubercles behind the 

 small but acute epibranchial 

 tooth; a small nick in the 

 margin anterior to the latter ohliteratum, sp. nov. 



sikkimense, Rathbun. 



Potamon (Potamiscus) decourcyi, sp. nov. 

 (Plate xvii, figs. 1-3.) 



The length of the carapace slightly exceeds three quarters of 

 the breadth and its depth is rather less than half its breadth ; it is 

 decidedly convex fore and aft and slightly so from side to side. 

 The surface is pitted and a little roughened. The antero-lateral 

 portions are strongly tuberculo-rugose, as are also, but to a less 

 marked extent, the anterior regions behind the epigastric and post- 

 orbital crests. On the side walls are fine oblique striae which 

 pass across the postero-lateral border. 



The cervical groove is well marked, though not deeply graven, 

 where it defines the mesogastric area ; but its lateral continuations 

 towards the orbits are almost entirely or entirely suppressed. No 

 trace of them exists in a very large male, but they are just percep- 

 tible as very faint and extremely shallow depressions in the younger 



