DUTCH BORNEO-EXPEDITION. 71 



the subgenera Parathelphusa and Geothelplmsa. It difiers 

 from the former by the existence of only one single epi- 

 branchial spine and by the absence of a postfrontal ridge, 

 for in Parath. spinigera White, the only form with one 

 epibranchial tooth, the lateral portions of the postfrontal 

 crest are well-developed and sharp. Perithelphusa may be 

 distinguished from Geothelphusa by the well-developed epi- 

 branchial spine and by the existence of a spiniform tooth 

 on the upper angle of the arms of the anterior legs. 



Potamon {Perithelphusa) borneensis v. Mart. var. 

 hilaris n. 



(Plate 5, fig. 4). • 



Thelphusa borneensis von Martens, in : Archiv fur Natur- 

 geschichte, 34 Jahrg., 1868, p. 18. 



Five specimens (3 cfcT, 2 99) were collected by Max Moret 

 at Sintang. 



The two females, though adult, carry no eggs. 



This interesting species bears some general resemblance 

 to Parath. spinigera White from Calcutta, but differs by 

 the absence of the postfrontal ridge. It appeared to me 

 probable that either this species or one of the two follow- 

 ing might belong to Potamon borneense v. Mart., and 

 therefore one male specimen of each was sent to Prof. 

 Hilgendorf at Berlin, who, after a close examination, wrote 

 me the following about the species which 1 go to describe: 

 »Diese Form kann zur Noth mit T. borneensis zusaramen- 

 gebracht werden. Ich würde aber doch jedenfalls eine 

 Varietat daraus machen". The individuals described by von 

 Martens have been collected near Seminis in the Sampas- 

 basin and at Lempai near the lake of Danau Sriaug, in 

 the Upper-Kapoeas-basin, in the same region therefore as our 

 specimens. The specimen sent to Berlin, was the male N° 2. 



Our specimens are of a larger size than those of 

 von Martens, the cephalothorax of the largest individual 



WotesB frotii the Leyden uMviseuin, Vol. XX.I. 



