6 Psyche [February 



main support of the pharynx. Just below these pharyngeal 

 struts the pharynx emits two other struts {ts^), one each side, 

 which proceed almost horizontally and posteriorly and fork, 

 sending a strut {ts"^) anteriorly to the base of the salivary-pump 

 or syringe {sp). This strut again forks and sends a strut its^) 

 anteriorly to the base of the labium {hi). Posteriorly (beyond 

 the first forking) the struts become broad and thin plates follow- 

 ing the sides of the pharynx, and attached to its outer walls by 

 tissue. The plates in transverse section are roughly V-shaped 

 (Fig. 12c?) and connected together by tissue; they enclose and 

 protect the setse. From the posterior end of the chitinous pharynx, 

 where the plates become broadest, they rapidly narrow to mere 

 tendons, which extend right to the occipital foramen, where the 

 tips of the two tendons broaden slightly, and attach to the occiput 

 near the attachment of the retractor muscles of the setae. In 

 more generalized forms, such as the Cicada, the posterior ends 

 of these seta-guides are connected by a transverse piece which 

 gives off two branches that are attached to the dorso-posterior 

 part of the head-capsule. This appears to indicate that the whole 

 structure is a modification of the tentorium to form a guide or 

 protection to the setse, and give support to the floor of the mouth 

 for the working of the salivary syringe. We therefore call this 

 arrangement of struts, plates and tendons the tentorial structure 

 its). 



The syringe, or salivary pump (sp), lies beneath the anterior 

 part of the pharynx and opens on the basal part of the labium 

 {hi), beneath the hypopharynx. The body of the syringe is cup- 

 shaped, and highly chitinous, with an inverted top, thinner and 

 more flexible, which forms a plunger. From the center of the 

 plunger rises a chitinous tendon or plunger-rod, around which are 

 attached the powerful retractor muscles {spm). These muscles 

 di\'ide slightly posteriorly and form two branches which attach 

 to the base of the occiput beneath the occipital foramen. The 

 two salivary ducts {sd), after entering the head, lie on the floor 

 of the head-capsule in the space between the two branches of the 

 syringe muscles, and join in a very short common duct just before 

 entering the syringe near the valve {v). This valve is formed 

 by a membraneous fold of the syringe wall, which covers a shallow 

 recess made by a bulge in the wall where the common duct enters. 



