NO. II NAIADS OF DRAGONFLY GENUS PLATHEMIS—LEVINE 5 
Seven elongate and two ovoid areas are present on the dorsal surface 
and are surrounded by numerous medium to long setae and short 
dark-colored spines. These glabrous spots are the areas of insertion 
of the gnathal muscles (Asahina, 1954). 
The COMPOUND EYES (eye) are situated on the prominent antero- 
lateral angles of the head. They are irregular in shape and, according 
to Lew (1933), composed of “three sets of distinctly distinguishable 
tissues.” Lew also notes that only the pigmented tissue on the pro- 
tuberant portion of the eye is functional. 
The postocciput (poc) forms the posterior rim of the cranium. It 
is a narrow U-shaped sclerite, with its ends terminating at the posterior 
tentorial pits. 
Of the suBcENaE, only the plewrostomae (pm) are present. Each 
pleurostoma is an extremely small, elongate sclerite arising at the base 
of the mandible and extending to the ventral exterior edge of the 
anterior tentorial pit. 
The GENAE (ge) are a pair of undifferentiated sclerites between the 
compound eyes and the antennal bases. 
The POSTGENAE (pge) are a pair of undifferentiated areas postero- 
lateral to the compound eyes. 
THE TENTORIUM 
The tentorium consists of a corporotentorium in the center of the 
head and three pairs of arms supporting it from different parts of the 
cranium. The anterior and posterior tentorial arms arise as invagina- 
tions of the cranial wall, while the small dorsal tentorial arms are 
outgrowths of the anterior tentorial arms. 
The ANTERIOR TENTORIAL ARMS (ata) arise from slits (at) between 
the compound eyes and the bases of the mandibles. From these points 
of attachment the anterior arms converge posteriorly to fuse with 
the corporotentorium in the center of the head. 
The POSTERIOR TENTORIAL ARMS (pta) arise from the posterior 
tentorial pits which are partially coincident with the anterior portions 
of the postoccipital suture. They are much stouter than the anterior 
arms. 
_ The DoRSAL TENTORIAL ARMS (dta) are shorter and narrower than 
those described above. Each dorsal arm arises from the mesal margin 
of the anterior tentorial arm midway between the anterior tentorial 
pit and the region of fusion of the anterior arm with the corporoten- 
torium. The dorsal tentorial arms are weakly attached to the cranial 
wall and are easily dislodged. 
