BY R. J. TILLYARD. 343 



Head square in front, with small prominent dark eyes at the 

 extreme antero-lateral corners; front fringed with a ridge of 

 irregular hairs; antennce seven-jointed(Plate viii., fig.4), first and 

 second joints from base short, stout and rounded, next four 

 longer and narrower, cylindrical, with pale tips; seventh (apical) 

 joint thin, sharply pointed; all segments furnished with irregular 

 hairs of varying lengths, and great fineness; ocelli inconspicuous, 

 in a small tiiangle on the rather flat epicranial surface; jjostocular 

 lobes full and well-rounded, hairy. The back of the head is of 

 irregular surface, so that mud and silt collect in ridges there, 

 giving the appearance, shewn in the Plate, of a slight colour- 

 pattern of light and dark brown alternately. (View of head 

 from in front is given in Plate viii., tig.3). Labium, in position 

 of rest, reaching to between the bases of middle and hind legs; 

 length, when closed, to base of mentum, 6-5 mm.; median and 

 lateral lobes of mentum when closed forming a nearly hemi- 

 spherical cup fitting close up to eyes and antennae; rest of mentum 

 projecting backwards more flatly; indentations of lateral lobes 

 fitting closely, and terminal hooks lying concealed along margin; 

 length of mentum 3 mm., greatest breadth 4-5 mm.; lateral lobes 

 1'8 mm. to base of terminal hook. Mentum broad, subtriangular, 

 with median lobe advanced to a blunt rounded apex; mental 

 setae, 5 primaiy, about 1 mm. long, 4 secondary, 0'2 to 0'3 mm. 

 long, on each side. Lateral lobes subtriangular, outer edge 

 strong, ridged, witli tiny stiff bristles arranged irregularly along 

 outer edge; five strong stiflf lateral setce springing from the inner 

 side of the ridge, from 1-2 to 08 mm. long; terminal hook just 

 above the top seta, very sharp, 1 mm. long; distal border strongly 

 dentate, there being generally seven distinct teeth on each side, 

 unsymmetrical, but arranged so as to fit one another accurately 

 when the mask is closed; teeth rounded, the larger ones tending 

 to overhang slightly on the lower side (" nodding "); largest 

 tooth, generally the middle one on the left-hand side, about 

 0"3 mm. broad by 02 mm. high (Plate ix., tig. 1). Thorax: 

 Prothorax short and broad, with protruding lateral angles. 

 Meso- and metathorax well-formed, fairly smooth, dark brown 



