THE SUBFAMILY LIBELLULIN^. 301 



the extremities, nodal and subnoda). sectors undulating in the middle, the intermediate 

 cells bisected towards the hind margin ; hind wings broader than the fore wings, with 

 12-15 antenodal and 15-17 postnodal nervures, the first three postnodals not con- 

 tirmous, triangle free, followed first by three rows of cells and then by a series of two, 

 increasing, no supratriangular nervures, one cross nervure in the lower basal cell, 

 sectors of the triangle united at the base : anal appendages of the male as long as the 

 ninth segment, rather slender towards the base, then thicker and a little depressed, the 

 lower appendage nearly as long as the others ; those of the second segment not con- 

 spicuous ; spines of the hind tibia? more numerous than in Lepthemis and slender. 

 Type IAbellula attenuate^ Eversm. 



Genus 64. Zyxomma, Ramb 

 (Head, Plate LV1I. fig. 10.) 

 Ramb. Ins. Neur. p. 30 (1842); Brauer, Verh. zool.-bot. Ges. Wien, xviii. pp. 364, 712 (1868). 



Eyes connected by a long suture as in Mslina ; face very hairy ; frontal tubercle 

 rounded above, entire ; abdomen very slender, longer than the hind wings, segments 

 2 and 3 inflated, and 2-4 carinated, dorsal and lateral carinas very slightly marked, 

 segment 8 not perfoliate in female : wings long and narrow, pterostigma moderately 

 long ; fore wings with 11-12 antenodal and 5-7 postnodal nervures, last antenodal and 

 first two or three postnodals not continuous, cells of the lower postnodal space simple, 

 triangle on the same plane as on the hind wings, slightly oblique, rather broad and 

 short, traversed by one nervure, and followed by three rows of cells, no supratriangular 

 nervures, nor more than one nervure in the lower basal cell, subtriangular space 

 consisting of three cells, sectors of the arculus stalked, arched at the extremities, the 

 lower one often a little irregular beyond the middle, nodal sector very slightly waved ; 

 hind wings not much broader than the fore wings, with 8 or 9 antenodal and 5-9 post- 

 nodal nervures, the last antenodal nearly always continuous, but the first two or three 

 postnodals not continuous, triangle free, followed by two rows of cells, sectors of the 

 triangle often slightly separated at base : anal appendages rather short. 



Type Zyxomma petiolatum, Ramb. 



Genus 65. Orthetkum. 



(Neuration, Plate LV. figs. 5, 6.) 



Newm. Ent. Mag. i. p. 511, note (1833). 



Ubella, Brauer, Verb, zool.-bot. Ges. Wien, xviii. pp. 368, 731 (1868). 



Hydronympha, Bucb. Syst. Ent., Odonata, p. 8 (1878). 



Frontal tubercle bifid; eyes contiguous in front; abdomen slender or moderately 

 broad, shorter or longer than the hind wings, the base always more or less thickened, 

 and sometimes inflated, segments 2 and 3 carinated, segment 4 sometimes a little 

 constricted at the base, segments 4-7 generally of nearly equal size, whatever the shape 



