May, 1916] Homopterous Studies. Part II 311 



run forward to the anterior edge of the clypeus; here they 

 attach to the dorsal region of the clypeus, and at the same time 

 are connected with one another by a narrow bridge, which is 

 scarcely visible. From the anterior region of the pharynx 

 two small tentorial structures attach to the anterior arms and 

 form the chief means of support of the pharynx. 



The posterior arms, the invaginations of which are con- 

 nected by the body of the tentorium (t. b.), run forward along 

 the ventral region of the head, as far as the salivary pumping 

 apparatus (s. p.), where they attach on either side to the 

 syringe. The body of the tentorium is very prominent and 

 on either side it forms a means of support for the maxilla, to 

 which it is attached. Its median portion supports various 

 muscles, including those of the salivary pump and the labium. 

 Passing up from the invagination, the posterior arms nearly 

 surround the occipital foramen and join with the corresponding- 

 dorsal arms. The connection is not so very prominent, and in 

 all the forms examined, the junction was confined to a mere 

 tendon. The dorsal arms, which are to be found beneath the 

 antennae, are quite prominent in the dorsal region of the head. 

 The size of the dorsal arms varies somewhat in different species ; 

 in Draculecephala mollipes they are short and branched, while 

 in Deltocephalus inimicus and Agallia sanguinolenta they 

 are much longer. Between the invaginations of the dorsal 

 and anterior arms, small tendonous plates are to be seen. 



In the Jassoid head, the correlation between the tentorial 

 structures and the appendages of the head is to be found and 

 forms the basis for their interpretation. 



Epipharynx—{Pl XX, Figs. 14, 1, 2, 3, 15). The anterior 

 end of the dorsal plate of the pharynx is differentiated into 

 the epipharynx (ep.), which is seen externally as the small peg 

 covering the base of the labium. This structure is closely 

 related to the labrum and in fact, the separation of the two 

 is a difficult matter. The pharynx (ph.) continues along the 

 under side of the labrum and passes out as the epipharynx. 

 The epipharynx is fused with the anterior edge of the labrum, 

 but a trace of the former condition can be seen. 



Hypopharynx — (PI. XX, Figs. 8, 15). The anterior end 

 of the ventral plate of the pharynx is the hypopharynx (hyp.) 

 and is a prominent structure in the mouth-cone of the Jassid.. 



