144 THE INTEGUMEXTAL SKELETON OF THE IMAGO. 



plate, the body, and of a process at its dorsal extremity. This 

 process is an elongated spoon-shaped scale, hence I shall term 

 it the ' cochleariform process ' ; but in profile it appears like a 

 curved hook (Fig. 28, 4, ch). The distal margin of the body 

 of the sclerite supports a number of chitinous folds, and a 

 treble row of bifid rods, the teeth of the prestomum. The 

 chitinous folds form the inner orifices of the pseudotrachea 

 and the lateral walls of the prestomum (Fig. 31). 



The ventral extremities of the bodies of the discal sclerites 

 are united by a thick nodule of black chitin, the nodulus 

 (Fig. 28, 4, n). The nodulus is connected with the furca by a 

 strong elastic ligament. 



The proximal margin of the discal sclerites is attached by a 

 loose syndesmotic cuticle with the distal end of the hypoglossa. 

 This cuticle forms a deep pouch. I shall term the pouch 

 the ' poculum ' (Fig. 31, p). The anterior proximal angle of 

 the body of the discal sclerite articulates with the end of 

 the paraphysis. 



The discal sclerites are parallel with each other when the 

 oral disc is flaccid and folded, and they are then flexed on the 

 paraphyses, so that the angle between the discal sclerite and 

 the paraphysis is acute. 



When the prestomum is open the paraphyses are separated, 

 and the discal sclerites diverge in front, and form a more 

 obtuse angle with the paraphyses. In this position the orifice 

 of the poculum is triangular, and the ligament between the 

 nodulus and the furca is stretched. 



The distal surface of the oral disc exhibits two lateral halves, 

 separated by a deep fissure, the prestomum, which may appear 

 as a mere median cleft when it is closed, or as a deep fossa 

 when open. 



Under slight violence the union between the two edges of 

 the pseudolabium, which extends from the dorsal margin of the 

 stomal disc to the junction of the middle and distal third of the 

 prelabrum, is ruptured. The bead in the left is drawn from 

 the furrow in the right edge, and the disc appears cordiform 

 instead of oval. The prestomum opens by this cleft on the 



