328 MONOGRAPH OF THE GENUS SYNTHEMIS, 



line of origin of the peculiar Chloro(jom2}hus so as to converge 

 towards Synthemis, since it exhibits a remarkable enlarge- 

 ment of the basal area of the hind wing, which, in its retention 

 of cross-veins, and in the form of its anal loop, bears considerable 

 resemblance to Synthemis. 



Such a diagram is not, of course, intended to exhibit accu- 

 rately the relative ages of the various archaic groups. These can 

 only be ascertained, if at all, by a careful study of their present- 

 day geographical distribution, coordinated with a knowledge of 

 the requisite geological data. 



Tiie result of this study of both nymphal and imagiual charac- 

 ters in Synthemis seems to me to demand imperatively a further 

 altpi'ation in the accepted classification of the Corchdiinoi (ficnfi. 

 lat.). There are, in the subfamily, three distinct groups : Syn- 

 themis with a distinct non-Gorduline tendency in the nymph; 

 Macromia with a distinct non-Cordidine (^Eschiiine) tendency in 

 the imago; and, finally, the Gorduliince, s.str., forming the greater 

 part of the subfamily, in which the true Gordidine characters of 

 both nymph and imago are developed. I do not suggest the 

 elevation of tlie.se three groups into subfamilies, simply because 

 I do not consider that the C ordidiiiuH {iiQXi&.\a.t.) ca.n ever be 

 themselves admitted to more than that rank — their Libelhdid 

 connection is so close and evident. I would therefore suggest a 

 division of the subfamily Cor(Z^<.^^^?^«;(sens.lat.) into tln-ee main 

 groups as follows : — 



i. Larvae with abdomen considerably rounded, but always longer 

 than wide, smooth; wing-cases parallel; head without frontal 

 horn, subtriaiigular in front, with eyes well behind tlie level of 

 the front; legs long and slender. 



Imagines with (when present) an elongated anal loojJ, having 

 a more or less distinct longitudinal bisector; triangle of hind- 

 wings very often recessed to, or neai-ly to, the level of arculus; 

 basilar space alwaj's free Group Cordidina. 



ii. Larvfe with abdomen very much rounded, nearly circular 

 when viewed from above, smooth, much flattened; wing-cases 



