8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
base of each mandible. In addition, a weaker abductor tendon (abt) 
is attached to the lateral margin of the base, close to the ventral con- 
dyle. The muscles inserted on these tendons have their origins on the 
cranium. 
The MAXILLAE (mx) are composed of two distinct portions; a 
basal part consisting of cardo and stipes, and an apical portion divided 
into two freely movable processes, here called the inner lobe and the 
outer lobe. The maxillae assume a position beneath the mandibles and 
lateral to the hypopharynx and are suspended from the head by a 
single point of articulation. 
The cardo is divided by an arcuate suture into two sclerites, the 
basicardo (bc) and the disticardo (dc). The dividing suture almost 
encloses the more proximal and convex disticardo close to the margin 
of the stipes. In the retracted position the cardo is folded dorsally 
above the stipes, where it articulates on the anterior margin of the 
posterior tentorial pit. 
The stipes (st) is the largest sclerite of the maxilla. The parastipi- 
tal region is undemarked from the remainder of the stipes. 
The inner lobe (il) has been generally regarded as representing the 
fused Jacinia and galea of more typical mandibulate insects (Tillyard, 
1917; Chao, 1953; Asahina, 1954), but Snodgrass (1954) has theo- 
rized that the galea has been lost and that the inner lobe represents 
only the lacinia. In Plathemis lydia this lobe typically bears, on its 
mesal margin, a subapical fringe of long setae and several long, sharp 
apical teeth, called laciniadentes (Iced) by Crampton (1923). In pro- 
traction of the maxillae the inner lobes are thrust forward beyond the 
mandibles to grasp the prey and pass it from the labium to the 
mandibles. 
The slender outer lobe (ol), arising at the distolateral angle of the 
stipes, has been interpreted as the galea by Crampton (1923), but 
numerous other workers regard it as the palpus of the maxilla. In 
the adult dragonfly the outer lobe is provided with two muscles, as 
shown by Snodgrass (1954). This, according to Snodgrass, identifies 
it as the maxillary palpus; a galea has but one muscle. The outer 
margin of this lobe bears many well-developed inwardly curving setae. 
A small sclerite, the palpifer (pf), is the actual area upon which 
the outer lobe takes its origin. 
The HYPOPHARYNX (hy) of Plathemis lydia is a large cushionlike 
lobe that projects downward between the anterior portions of the 
maxillae and is separated from the base of the labium by a wide 
membranous area between the maxillary stipites. It apparently con- 
sists only of the lingua; superlinguae are not present. The adoral 
