BUTCH BORNEO-KXPEDITION. 135 



mesogastric lobe and on the intestinal and posterior bran- 

 chial regions the puncta are very fine, numerous and 

 crowded ; on the rest of the surface the puncta are rare 

 and the transverse anterior branchial lobes, that are situa- 

 ted immediately behind the protogastric regions, are almost 

 smooth, devoid of puncta. The strongly declivous lateral 

 sides of the cephalothorax are covered with numerous obli- 

 que raised lines. 



The upper margin of the front is a little more 

 than half as broad as the distance between the extra- 

 orbital angles, the proportion of its breadth to the latter 

 is the same as in Ses. angustifrons. The four post-frontal 

 lobes, placed in a straight transverse line, are separated 

 from one another by rather deep grooves just as in Ses. 

 angustifrons ; they are prominent, though they do not 

 conceal the inferior margin of the front, when the cara- 

 pace is looked at from above. The internal lobes (Fig. 16«) 

 are once and a half, in Ses. angustifrons (Fig. 17) al- 

 most twice as broad as the external ; they are rounded and 

 almost smooth. The front (Figs. 16«and 16*) that is a little 

 concave and vertically deflexed downwards, making a right 

 angle with the upper surface of the cephalothorax , is 

 almost 4- times as broad as high in the middle ; it has a 

 somewhat different form in both species. The lateral mar- 

 gins, indeed, that are parallel with one another in Ses. 

 angustifrons, slightly converge in Ses. Amphinome and the 

 inferior margin is a little arcuate. The latter presents a 

 slight, moderately broad emargination in the middle, in 

 Ses. angustifrons (Fig. 1 7) the median sinus is much 

 deeper; in a front- view of the cephalothorax this median 

 emargination is also visible, in the other species not. On 

 each side of the median sinus one observes on the front 

 a transverse ridge, about as broad as the inner post- 

 frontal lobes and contiguous to the lower margin of the 

 front; these ridges that do not reach the lateral angles of 

 that margin, are quite absent in Ses. angustifrons. 



In the middle the front appears somewhat granular. lu 



Notes from the Leyden IMuseum, Vol. XXI. 



