2 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.66. 



Amongst old world genera it is rivaled only by Atnphicnenhis for 

 extreme delicacy, though structurally it does not seem particularly 

 closely allied to that genus. 



The species are probably abundant in suitable localities, and it 

 is likely that several new forms await discovery. The fragility of 

 papered specimens makes it difficult in many cases to determine 

 satisfactorily the more minute details of structure, more especially 

 the anal appendages of the male. Hence it is often difficult to give 

 adequate descriptions or clear figures of these structures. Moreover, 

 in papered specimens the colors are very likely to be faded, so that 

 the discrimination of species is not always an easy matter. 



The genus may be defined as follows : A coenagrionine genus, with 

 short tibial spines and a rounded frons. Wings petiolated to level of 

 ac, this lying about halfway between the first and second antenodals. 

 Costal margin of quadrangle about one-third the length of the anal 

 maroin in 5ie forewing, about one-half in the hind wing. Rs aris- 

 ing ^from vein descending from nodus, M3 from a point imme- 

 diately proximal to it. Pterostigma of forewing distinctly larger 

 than that of hind wing. Female with spine at apex of eighth sternite 

 of abdomen. Male wi^th apex of terminal segment deeply emargmate 

 and slightly elevated. Upper anal appendages more or less bifid, 

 lower appendages rather flattened, each of these latter carrying on 

 its upper part a thickened process which may be separated by a 

 cleft from the rest of the appendage so as to stand out from it as a 

 strong conical spine. 



In the species examined for this structure the penis has the distal 

 part of the shaft armed with fine lateral spines. The third segment 

 (employing Kennedy's nomenclature) has a well-developed internal 

 fold ; the terminal fold is present but reduced. The inner surface 

 of the distal lobe of the third segment is armed with a number of 

 fine shagreenlike denticles, and the lateral margin of this lobe carries 

 a strong spine on either side. Its apex may be cornuate {A. lor- 

 neensef or simple and rounded (.4. hisopa). Lastly, the coloring of 

 the two sexes is similar, no dimorphic females have been known to 

 occur, and postocular spots are present. 



The relationship of the genus is evidently with the Enallagma 

 series of genera. It resembles them in the shape of the frons, in the 

 presence of a spine on the eighth segment of the abdomen of the 

 female, in the similar coloring of the two sexes, and in the post- 

 ocular markings. It differs, I think, from all of them in the greater 

 amount of petiolation of the wings, and in the extremely slender 



build of the body. 



It resembles some of the American species of Enallagma, and the 

 African Proischnura subfurcatum (de Selys) in having the pteros- 



