HANSEN AND SÖRENSEN, THE TARTARIDES. 9 



the palp the mandible is produced forwards into a triangulär 

 process which is its »pars manducatoria». The mandibles 

 tonch each other in the mesial Hne from their base forwards 

 to a point situated a little longer from their origin than from 

 the tip of the manducatory part; along that proximal portion 

 they are connected by exceedingly narrow, linear, membra- 

 nous skin allowing them a feeble see-sawing movement. In 

 the distal portion their inner margins diverge gradually some- 

 what towards the end; the inner surface of this part is 

 clothed with long, plumose hairs. Seen from the side, the 

 mandibles show a considerable depth. Seen from above, the 

 long free portion of both mandibles together presents a pecu- 

 liar shape ; in about two-thirds of the whole length from their 

 base to the tip of the manducatory part the upper wall of 

 the mandibles is membranous and sloping, the outer margin 

 lying considerably higher than the inner one at the mesial 

 line of the animal. Furthermore the upper walls of both 

 mandibles are so completely fused that even no suture is found. 

 In this way an oblong space is formed between the upper 

 walls of the tAvo mandibles, and in the posterior half of this space 

 the labrum is found. The upper lateral margin of each man- 

 dible is very strongly chitinized and produced backwards into 

 a strong, rather long process lying in the head; from these 

 processes muscles moving the mandibles originate. 



Labrum itself is rather large, oblong and thick ; it tapers 

 anteriorly, and its rounded distal end reaches slightly in front 

 of a line drawn between the insertion of the palps. 



The upper wall of the cavity of the mouth is thus for- 

 med by the labrum, while the floor is the upper surface of 

 the mandibles; this floor shows a beautiful equipment with 

 a great number of moderately short hairs regularly arranged 

 in lines crossing each other. In front of the cavity of the 

 mouth a kind of fore-court is found between the two mandu- 

 catory parts equipped with long plumose hairs and the lower 

 margin of the antennse above these manducatory parts. It 

 must be added that the upper surface of the labrum is rather 

 firm and glabrous in the proximal part, while its distal part 

 is membranous and adorned with long hairs; the lower sur- 

 face has at the middle two large, transverse tufts of very 

 long simple hairs (Ph 1, fig. 1 i). 



