(10) 

 404 C. GORDON HEWITT. 



anterior end of which two arms diverge and form the chief 

 skeletal structures of the oral lobes. The lower end of the 

 theca rides on this structure, the bottom of the sinus resting 

 on the median rod, and the two-pointed lateral terminations 

 of the theca rest on the arms. In this manner these pro- 

 cesses, in a state of repose, keep the arms of the f urea closely 

 approximated. The result of this will be seen later in study- 

 ing the musculature of the proboscis. 



The sides of the haustellum are membranous. On its 

 anterior face, in a groove formed by the overlapping mem- 

 branous sides, lie the labrum-epipharynx and labium-hypo- 

 pharynx. The labrum-epipharynx (figs. 1 and 3, Lep.) is 

 attached at its proximal end to the membranous rostrum, but 

 is incapable of a labral-like movement on account of its close 

 connection with the labium-hypopharynx. Two slightly- 

 curved, hammer-shaped apodemes (fig. 1, ap.) are attached 

 to the proximal end of the labium-epipharynx. They assist 

 in folding the proboscis during retraction, as will be shown 

 later. The labium-epipharynx is shaped like a blunt arrow- 

 head; the external surface is somewhat flattened. It is 

 composed of two pairs of sclerites, an outer pair enclosing an 

 inner pair, which form the pharyngeal channel. The edges 

 of the inner tube are connected by a groove with the hypo- 

 pharyngeal portion of the labium-hypopharynx, as shown 

 in fig. 3. The labium-hypopharynx (fig. 3) represents the 

 fusion of the hypopharynx with the greatly modified and 

 fused second maxillae or labium. It consists of a sclerite, 

 curved in section, having the chitinous hypopharyngeal tube 

 (fig. 3, hp.) fused to it along the upper half of its length. 

 The edges of the hypopharyngeal tube engage with those of 

 the inner pair of sclerites of the labium-epipharynx, as men- 

 tioned before. Distally the hypopharyngeal tube becomes 

 free from the labium, as shown in fig. 3, and ends in a point 

 where the lingual salivary duct opens. 



Down each side of the labium-hypopharyngeal sclerite a 

 rod-like thickening runs. Distally these thickened margins 

 (paraphyses of Lowne) articulate with the discal sclerites. 



