REPORT ON THE PELAGIC HEMIPTERA. 27 



the third joint, but in the hxtter the furrow is finely transversely wrinkled. The integu- 

 ment of the fourth joint has several rows of a few rather stout hairs with tubercled bases. 



The Mandibles (PI. III. fig. 4) seem to be triquetrous, with one side broader than 

 either of the other two, and are scarcely dilated at the apex, which is very hard but not 

 extremely finely pointed. On the outer edge, between the narrow sides, is a row of saw- 

 like, back-pointing teeth of unequal length. These teeth gradually increase in length 

 from the apex backwards, the fifth or sixth being the longest ; after that they rapidly 

 decrease in length till they become little more than slight elevations of the edge of 

 the mandible. In number they vary in different species, but the average number is 

 probably about twelve. In one species {wullerstorffi) the breadth of the mandible a 

 little behind the apex and across the narrower side is about '012 mm. and on the broader 

 side about "024 mm.; in another species (sericeus), the breadths are respectively about 

 •012 mm. and "018 mm. The mandibles can be traced back from the base of the rostrum 

 into the head. On entering the head they suddenly diverge, the space between them 

 being about as broad as the base of the rostrum. They then go nearly straight back- 

 wards to a point on a level with the base of the autenniferous tubercles, and are then 

 suddenly bent forwards and outwards, the portion after the abrupt bend being either 

 gradually dilated or split into several portions which diverge a little. This is the appear- 

 ance presented by specimens mounted in Canada balsam, and lack of material has unfor- 

 tunately prevented me from attempting to dissect out the parts. 



The AlaxiUce (or the organs which in the Hemiptera are supposed to represent the first 

 pair of maxillye) are much more complex in structure than the mandibles. Though often, 

 like the mandibles, protruded from the apex of the rostrum, they can be retracted at least 

 so far as that their tips reach only to the apex of the third joint of the rostrum. Thgugh 

 not inseparably united to each other, the two maxillae are yet for a considerable portion 

 of their length so closely connected that they form but one organ. Moderately magnified 

 and viewed directly from above, this appears to be a rather blunt and stout bristle lying 

 between the mandibles, but when a higher magnifying power is used, the structure is 

 seen to be rather complex. As the specimens which I have examined are mounted in 

 Canada balsam, and all the parts do not lie in the same plane, and as moreover I have 

 not had an opportunity of making transverse sections, the following description (made 

 with the aid of an amplification of 900 diameters), is probably only approximately correct. 

 Viewed from above the organ presents the appearance of four parallel lines, the distance 

 between the inner two being rather greater than between the outer and inner on either 

 side (PI. III. fig. 5). Towards the apex the outer and inner line on each side approach 

 each other, and form a point which curves rather abruptly inwards, the point on one side 

 overlapping and touching the point on the other, thus forming a rather blunt apex 

 to the organ. On the outer edges, from the tip for a considerable way backwards, are a 

 series of fine, rather irregular hairs, at first directed outwards and a little backwards, and 



