NO. II NAIADS OF DRAGONFLY GENUS PLATHEMIS—LEVINE 13 
mesothoracic anepisterna. It is separated from the latter, and also 
from the wing bases and the scutum, by a membranous area. 
The scutum (sct.), the largest sclerite of the tergum, is a longi- 
tudinally elongate, posteriorly convergent, weakly sclerotized lobe in 
the membranous region between the anterior wing bases. Its posterior 
margin is fused with the scutellum. Numerous tiny posteriorly- 
directed spines are present on the dorsal surface. 
The scutellum (sclz) is a small hemispherical lobe just posterior to 
the scutum. Its anterior end is undemarked, but its posterior margin 
is arcuate and continuous laterally with the axillary cords (axc,) of 
the basal wing membrane. Setae of various sizes are scattered over the 
scutellar surface. 
METANOTUM: The metathoracic tergum (fig. 14) consists of a 
single transversely elongate sclerite, the metanotum (ng), which is 
situated between the posterior wing bases. The metathoracic tergal 
apophysis is represented by a shallow pit (tag) on its anterior margin. 
Numerous short setae are borne on the median dorsal surface. 
THORACIC PLEURA 
The thoracic pleura (figs. 14, 16, 17) are relatively large and greatly 
modified and consist of propleuron, mesopleuron, and metapleuron. 
PROPLEURON: The prothoracic pleuron is composed of two regions, 
the episternum and the epimeron, which are somewhat separated by 
a shallow vertical depression lying above the pleural coxal process 
(cxp,). The pleural suture is lacking. 
The episternum (et,) is a relatively very small area bounded an- 
teroventrally by the precoxal bridge and posteriorly by the epimeron. 
Neither of the delimiting sutures is entire. The marginally setiferous 
precoxal bridge (pr) is well sclerotized and united ventrally with the 
basisternum. 
The epimeron (em,), the largest portion of the propleuron, is 
fused with the pronotum. It is posteriorly separated from the meso- 
thoracic katepisternum by the peritremal plate of the mesothoracic 
spiracle above and a flexible, folded, partially sclerotized area below. 
MESOPLEURON: The mesothoracic pleura are much more highly 
developed than the prothoracic pleura. Each pleuron is divided into 
two main regions, the episternum and the epimeron, by the pleural 
suture (pls.), which extends obliquely posterodorsad from the pleural 
coxal process to the wing base. The episternum is further divided by 
a well-demarked transverse suture into two secondary regions known 
as anepisternum and katepisternum. 
