Q PREFACE. 



The following grouping is the best that can he made at present : — 



Mask tlat (agreeing with Agrioniua), — all yEschnina and Gomphina (except Cordu- 

 legaster). 



Mask, spoon-shaped (agreeing with Libellulina), — Cordulegaster. 



Antennte, four-jointed and flattened, — Gomphus and Allies. 



Antenna; filiform and seven-jointed, — Cordulegaster and ^Eschnina, exceptmg two 

 aberrant genera having six and five joints. 



All legs with tarsus three-jointed, — ^schnina and Cordulegaster. 



All legs with tarsus two-jomted, — Ictinus. 



The two anterior pairs of legs with tarsus two-jointed, — Gomphma. 



These general characters are sufficient to determine the place of any nympha. 

 August, 1881. 



