10 THE IMMATURE STATE OF THE ODONATA. 
somewhat semicircular space, and consists of the following parts: a trans- 
verse short part, representing the front of the imago, separated by a well- 
marked border from asimilar space, representing the epistoma and rhinarium 
joined in front to the large transverse upper lip, the front part of which is 
larger than the base and has oblique sides. On each side next to the upper 
lip, the base of the mandibles is visible. The mandibles, maxille, and tongue 
offer as far as observed no special characters. Mask flat, long, covering the 
mouth parts beneath, as far as upper lip; extending to between middle legs, 
except in Gynacantha, in which it extends to hind legs. The fore border is 
‘always broader than base, never more than twice as large, and the whole 
mask is more or less gradually enlarged forward. Side bent up and narrowly 
marginated, The middle third of fore border is produced and more or less 
rounded, sometimes forms an obtuse angle, and is always cleft, generally not 
deeply, —in Gynacantha more deeply, surmounted by a comb of small hairs ; 
on each side the cleft there is sometimes a small tooth, which in Gynacantha 
is strongly developed. Palpus consists of a narrow, nearly straight lobe, 
either straight at tip or slightly rounded, produced at inferior angle in more 
or less developed tooth, and more closely meeting the opposite one. The 
inner edge is either smooth or finely denticulated ; movable hook, strong, 
rounded, very sharp, somewhat bent towards the tip and generally reaching 
the base of opposite one, and exceptionally it either extends beyond the base 
of opposite or does not quite reach it. Prothorax small, rather convex, 
rounded behind, more or less produced at the sides; the stigmata are large, 
open, and transverse, placed behind the prothorax and not covered by it; 
except in the La Guayra specimen, in which they are completely covered. 
The sides of the prothorax are produced above the fore legs in two processes, 
more or less divided and of varying proportion to each other. The form and 
size of these processes, being mostly rather distinct in form and size in the 
different species, seem to afford good specific characters. Analogous but less 
developed processes are found above the middle legs, and indications of them 
above the hind legs. Legs equally distant at base, or so nearly as not to give 
any character of importance, except in the La Guayra species, in which the 
hind legs are markedly more distant at base. Legs slender, not reaching tip 
of abdomen; femora and tibiwe of nearly equal length; tarsi half length of 
tibie, three-jointed ;—basal joint very short; claws strong, bent, sharp. 
Thorax comparatively small. Wing cases large, reaching fourth segment 
or beyond. 
