OF ARTS AND SCIENCES. 37 



The genus Plathemis, like Libellula, is characterized by the 

 sinuous nodal sector, which is distinctly waved, but is readily dis- 

 tinguished by the pair of ventral hooks on the first abdominal 

 segment of the male. Trimaculata, representing this genus, is 

 comparatively common but difficult to capture. One male in col- 

 lection. Length, 48 ; alar expanse, 70. 



13 Celitlieinis Hagen. 

 Calvert, p. 224; Hagen, Syn. Neur. N. A. p. 147. 



33 Celitlieiiiis ornata Rambur. 

 Calvert, p. 261 ; Hagen, Syn. Neur. N. A. p. 182.' 

 Rare. One female. Length, 42 ; alar expanse, 59. 



33 Celitliemis elisa Hagen. 



Calvert, p. 261 ; Diplax elisa Hagen, Syn. Neur. N. A. p. 182. 



The specimens of this beautifully marked species were taken at 

 Beaver Pond, in Derry, where it is not uncommon. Male and 

 female in collection. Length, 44 ; alar expanse, 56. 



Leucorliiiiia Brittinger. 

 Calvert, p. 224. 



34 Leucorliinia iiitacta Hagen. 



Calvert, p. 262 ; Diplax hitacta Hagen, Syn. Neur. N. A. p. 179. 



Abundant throughout August. Male and female in collection. 

 Length, 31 ; alar expanse, 51. 



15 Diplax Charpentier. 

 Calvert, p. 224; Hagen, Syn. Neur. N. A. p. 173. 



35 Diplax rubicuiiclula Say. 



Calvert, p. 262 ; Hagen, Syn. Neur. N. A. p. 176. 



The most abundant of all the Anisoptera. Male and female in 

 collection. Length, }^i ; alar expanse, 50. 



36 Diplax seniicincta Say. 



Calvert, p. 263 ; Hagen, Syn. Neur. N. A. p. 176. 



