DUTCH BORNEO-EXPEDITION. 101 



tively longer than in the female from the Upper Sibau and 

 in consequence of it the front of the latter appears slightly 

 broader. When the carapace is looked at from above, the 

 median sinus of the frontal margin appears, in Fot. sinuati- 

 frons, a little deeper than the lateral ones (Plate 8, Fig. 9^^) ; 

 in the female from the river Sibau, however, the free bor- 

 der of the front appears almost straight in the middle, but 

 the lateral sinuses are well-defined (Plate 6, Fig. 10«). The 

 postfrontal ridge almost fully agrees with that oï Pot. sinua- 

 tifronSi the median or internal portions, however, are cris- 

 tiform, in the type-specimens of the other species indistinctly 

 so. The oblique grooves between the gastric and the epi- 

 branchial region are somewhat deeper than in Pot. sinua- 

 tifrons and the cardiac area is bounded posteriorly by a 

 transverse depression from the intestinal one. In both spe- 

 cies are the epigastric lobes distinctly defined posteriorly 

 by a transverse furrow. The raised line above the legs of 

 the 5*15 pair is more prominent than in the other species. 

 As regards the course of the lateral margin of the cepha- 

 lothorax, the form of the extra-orbital tooth and of the 

 epibranchial one, the proportion between the distance of 

 these teeth from one another and that between the external 

 orbital angles, the female from the Upper Sibau agrees with 

 Pot. sinuatifrons. The free border of the front and the 

 supraorbital margin are almost smooth, but in Pot. sinua- 

 tifrons distinctly crenulate. 



Though the type-specimens are varnished , the upper 

 surface of the cephalothorax seems, however, to present the 

 same structure in both species. The anterior branchial region 

 is covered with oblique rugosities that, near the postero- 

 lateral margins, gradually pass into less salient, short, 

 raised lines. The extra-orbital tooth is granular above, the 

 front finely granulate. The epigastric lobes and the proto- 

 gastric regions appear very slightly rugose anteriorly, the 

 rest of the surface is minutely punctate. 



The inferior orbital margin is distinctly crenulate in Pot. 

 sinuatifrons, but in the female from the upper Sibau scar- 

 Notes from the Leyden JMuseum, Vol. XXI. 



