DUTCH BOIRNEO-EXPEDITION. 93 



reach the postfrontal ridge at the end of the lateral cristi- 

 form portions, about 5 millimeters internally to the epi- 

 brauchial teeth. The mesogastric furrow is narrow, does 

 not pass ou to the front and bifurcates posteriorly into 

 two faintly defined, parallel grooves, that are situated 

 close together and reach only to the middle of the gastric 

 region, so that, just as in Pot. sijiuatifrons, the mesogastric 

 area is not defined anteriorly. This area is rather small 

 and in proportion to the width of the cephalothorax a 

 little less broad than in Fot. sinuatifro?is : in the latter 

 species it measures about one fourth, in Pot. mahakkamense 

 only one fifth the width of the carapace. The rugose 

 urogastric areolets, that are not contiguous, are well- 

 defined, but the depressions bounding the cardiac region 

 are very shallow and iudistinct. The anterior branchial 

 region, twice as large as the posterior, is almost not se- 

 parated from the latter; a shallow groove bounds the 

 posterior branchial region posteriorly, just in front of a 

 raised line, that runs close to and parallel with the lateral 

 parts of the posterior margin and that ends above the 

 legs of the fifth pair. The distance between the external 

 orbital angles measures little more than half the breadth 

 of the carapace. The free border of the front (Fig. 8*), that, 

 like the upper margins of the orbits, is obscurely crenulated, 

 measures scarcely one fourth the width of the cara- 

 pace; it shows in the middle a broad shallow bay, which 

 is about half as broad as the frontal margin, but which, 

 in Pot. sinuatifrons (Fig. 9«) is a little less broad ; the la- 

 teral sinuses are almost indistinct. The outer angles of the 

 front are moderately sharp, the lateral margins are a 

 little oblique, slightly divergent; they make, however, 

 right angles with the contiguous parts of the free border, 

 because the latter are somewhat oblique. The lateral mar- 

 gins of the front curve regularly into the external por- 

 tion of the orbital margin and these external portions run 

 somewhat obliquely forwards. 



The interrupted post-frontal ridge resembles that of Pot. 



Notes troin the I-ieyden Museuxu, Vol. X^I. 



