HEAD, MOUTH-PARTS, ORTHOPTEIL\ EUPLEXOPTERA 275 



median ridge. The subgusta is broad, membranous, and pro- 

 vided with a shallow, median, longitudinal furrow. The hypo- 

 pharynx is the subquadrate structure cephalad of the constric- 

 tion of the parapharynx. Its dorsal surface is Comdex, slightly 

 elevated on the meson, and is densely covered with spinulae. 

 The distal end of hj^popharynx is also spinulate. There is an 

 elongated, triangular, slightly chitinized area cephalad of and 

 indefinitely separated from each lingula. The salivia is the large 

 lanceolate sclerite, ventrad of the cephalic part of the lingula 

 and the triangular area cephalad of it. It extends cephalo- 

 dorsad to the caudal margin of the distal spinulate area. Its 

 caudal third is strongly chitinized, its caudal third moderately, 

 and its middle third only slightly. This sclerite bears several 

 spine-like setae. The ventrocaudal angle of each salivia is 

 rounded and produced into a chitinized, tapering bar w^hich 

 extends ventro-caudo-mesad and meets the one from the other 

 side, forming a deep semicircular structure. The salivos is lo- 

 cated cephalad of this median structure. Each ventrolateral 

 angle of the hypopharynx, ventrad of the salivia and cephalad 

 of the bars supporting the salivos, is obtusely rounded and mod- 

 erately chitinized. The ventromeson of the hypopharynx is 

 concave, the concavity widens caudad, and is provided with a 

 shallow median furrow. On each side and cephalad of the 

 salivos is a pit leading into a short blind pouch which Mangan 

 ('08) has suggested to be a 'salivary receptacle,' but its function 

 has not been determined. The oscula is the membranous area lo- 

 cated ventrad of the hypopharynx. It extends laterad and then 

 dorsocaudad and is continuous with the labacoria and lingula. 

 The salivos is protected by a portion of the oscula which extends 

 ventrocephalad of the salivial bars. The salivary duct is large 

 and extends caudad for some distance before bifurcating. 



The general plan of the organization of the prepharynx in all 

 the genera studied manifests a striking similarity, and the homol- 

 logy of each component part is demonstrable wdth a fair degree of 

 certainty. The differences in size, shape, and position in these 

 structures, though great in some cases, are reducible in general 

 to a gradual series of modification. 



