208 
[October 
with the following exceptions, which are peculiar to the subfamilies 
Calopterygina and Agrionina.—The triangles, (t and discoidal 
and internal) entirely disappear, and the submedian vein (//) is con¬ 
tinuous with its prolongation (??,, the first or upper sector of the triangle) 
without being angulated and osculating with the postcostal vein (c) at 
the lower angle of the triangle (t) in order to form one side of that tri¬ 
angle, as is the case in the other four subfamilies, including of course 
Gomphus. — ‘‘Ind. The “ area above the Triangle” (Z)) (es^pace au Zc,s.s?/.s- 
du Triangle) assumes the form of an elongated, but more or less irregu¬ 
lar, parallelogram in Calopterygina and in certain genera of Agrionina 
(e. g. Megaloprepus, Palaemnema, Protonevra and Trichocnemis,) or of 
an elongated trapezium with its upper side shorter than its lower side, 
in the remaining genera of Agrionina. This difference arises from the 
lower side, i.e.the side facing the anal angle (2:), being always greatly 
elongated in both subfamilies, and the side adjoining the Triangle (t) 
being greatly shortened and made subparallel with the side facing the 
base of the wing in Calopterygina and in the exceptional genera of 
Agrionina, or elongated and directed towcirds the basal portion of the 
costa in the remaining genera of Agrionina. Thus modified this area 
is called ‘‘the quadrangle” or “the quadrilateral.”— ard. In conse¬ 
quence of the above modifications, the upper and lower sectors of the 
triangle {n and o,) which still retain the same name, spring immedi¬ 
ately from the upper and lower corners of the “ median area” (.:r), the 
triangles which intervene in the other four subfamilies being obsolete 
and there being consequently no osculation of d with e. 
