DUTCH BORNEO-EXPEDITION. 8l 



region ; the declivous lateral parts are coarsely punctate, 

 scarcely wrinkled. The cervical groove is interrupted, just 

 as in the preceding species and in both equally far dis- 

 tant from the anterior margin of the front ; the posterior, 

 median, crescentic portion is deep, the anterior portions 

 are just as deep as in Pot. borneense var. hilaris, hut iheiv 

 direction is less oblique: these furrows, indeed, 

 when continued backwards would form a right angle 

 with one another in the preceding species, but an acute 

 one in Potamon Büttikoferi. The gastric region is not 

 subdivided and even the anterior prolongation oftheraeso- 

 gastric area is not defined, the mesogastric furrow being 

 short and not bifurcating; the antero-external parts of the 

 gastric region appear, in the adult, somewhat wrinkled, 

 the ramifying wrinkles diverge from the anterior branches 

 of the cervical groove, in the younger individuals these 

 wrinkles are less conspicuous. The urogastric areolets agree 

 with those of Pot. bornemse^ and shallow depressions sepa- 

 rate the anterior branchial lobe from the posterior one, that 

 is considerably smaller, and the latter from the cardiac 

 region. 



The front presents distinctly a broad, shallow bay 

 that extends till the rounded lateral angles, which pass 

 with a curve into the upper margin of the orbits, so that 

 it is here also somewhat difiicult to measure exactly the 

 breadth of the free border of the front: it is about one 

 fourth the greatest width of the carapace. The somewhat 

 raised lateral margins of the front are slightly less 

 oblique than in Pot. hor^ieense var. hilaris^ so that the 

 front appears at the base a little less broad in proportion to 

 the width of the frontal anterior margin. Just before the 

 foveate epigastric lobes the surface of the front is marked 

 with a few transverse rugosities, but for the rest it is 

 coarsely punctate. The supra-orbital margins are sinuous 

 and form almost right angles with the outer margin of 

 the extraorbital tooth ; the outer angles of the orbits are 

 moderately sharp and reach almost as far forward as the 



Notes from the Leyden ]Museum , Vol. XXI. 



