302 ROBERT E. SNODGRASS. 



geal sclerite is a thick, densely chitinized, cup shaped sclerite loca- 

 ted in the ventral wall of the oesophagus a short distance back of 

 the mouth opening. The cavity makes a depression in the floor of 

 the oesophagus, and the sclerite is probably simply a thickening of 

 the oesophageal intima. Its shape varies in different species, but 

 viewed from above or below it is usually shield-shaped or oval, with 

 two elongate anterior arms and a small median posterior projection. 

 In Peripsocus californicus (tig. 16, oe. scl.) the anterior arms are 

 short, but there are two wide, expanded, plate-like arms projecting 

 posteriorly and outward. 



From the anterior end of the cavity of the sclerite a duct extends 

 forward, which soon divides into two. These ducts (fig. 16, d.) 

 continue anteriorly within the hypopharynx and then diverge out- 

 ward and turn posteriorly to become attached to the lingual glands 

 (gl. ) whose outer edges they traverse. The lingual glands are oval 

 or elongate-oval organs, with a thick chitinous lining, lying within 

 the base of the hypopharynx. They are the structures called by 

 Enderlein (13, 14) the " paraglossse " of the "endolabium." Each 

 gland is supported on a chitinous peduncle (fig. 16, ped.), which 

 projects posteriorly toward the caudal wall of the head to which it 

 is connected by means of muscles. 



III. The Mouth-parts of the Mallophaga. 



The mandibles (figs. 4 and 8) are always large and strongly 

 chitinized. In the Amblycera they are horizontal and parallel with 

 the head ; in the Ischnocera they hand downward sometimes per- 

 pendicular to the plane of the head. They are nearly always two- 

 toothed distally and usually have some sort of mesad projection 

 from the inner angle of the base. 



The maxillm (figs. 2 and 5) consist each of a rather large basal 

 piece (ffl«.) representing the stipes or stipes and cards, which *is 

 always fused with the lateral edge of the labium, of a simple, small 

 apical lobe, and in the Amblycera of a 4 segmented palpus. On 

 account of the union between the stipes and the adjacent edge of 

 the labium the palpi have the appearance of belonging to the 

 labium, and when the mouth-parts are dissected away from the head 

 the labium, stipes and palpi generally come off together. On 

 account of this the labium has been described by Grosse (5), and 

 the present writer (8 and 10) as possessing two 4-jointed palpi in 



