THE SUBFAMILY LIBELLULIN^. 295 



triangle free, its base on a level with the arculus, followed by two or three rows of cells, 

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

 of the triangle rising from a point : spines of the legs slender, rather long : anal 

 appendages of the male as long as the ninth segment, the lower appendage hardly 

 shorter; appendages of the second segment conspicuous, the hamulus terminating in 

 a slender double hook. 



Type Tyriohapta torrida, sp. n. 



Genus 53. Hejiistigma, g. n. 



Frontal tubercle convex ; eyes contiguous in front ; abdomen slender, as long as the 

 hind wings in the male and a little shorter in the female, hardly thickened at the base, 

 segments 2 and 3 strongly carinated, segment 8 not perfoliate in female : wings long, 

 narrow, and rather pointed, pterostigma long, the basal third always pale ; fore wings 

 with 10-14 antenodal nervures and 8-10 postnodal nervures, the last antenodal and the 

 first two or three postnodals not continuous, cells of the postnodal area simple, triangle 

 moderate, on a level with that of the hind wings, free, or traversed by one nervure 

 (exceptionally two), followed by three rows of cells, increasing, or two increasing, or three 

 followed by a series of two increasing, the base hardly oblique, generally one supra- 

 triangular nervure, one cross nervure in the lower basal cell, sectors of the arcuhis 

 stalked, more or less curved at the extremities, nodal sector only waved at the base, the 

 subnodal hardly at all, the intermediate cells bisected towards the hind margin ; hind 

 wings broader than the fore wings, with 7-8 antenodal and 8-10 postnodal nervures, 

 the first two or three subnodals not continuous, triangle free, its base on a level with 

 the arculus, and followed by two rows of cells, increasing, or two and then one, 

 increasing, a supratriangular nervure only exceptionally present, one (rarely two) cross 

 nervures in the lower basal cell, sectors of the triangle united at base : anal appendages 

 of the male slender, as long as the ninth segment, the lower one nearly as long as the 

 others ; appendages of the second segment moderately conspicuous. 



Type Libellula albij)mxcta, Ramb. 



Genus 54. Thekmochoeia, g. n. 

 (Plate LII. fig. 8.) 

 Characters of Eemistigma. Abdomen more distinctly thickened at base, pterostigma 

 shorter, unicolorous; fore wings with 16-17 antenodal nervures and 10 postnodal ner- 

 vures, the last antenodal and the first two postnodals not continuous, triangle traversed, 

 followed by three rows of ceUs, and a series of two increasing, two supratriangular 

 nervures, three cross nervures in the lower basal cell, sectors of the arculus hardly more 

 cui-ved at the extremity than the nodal and subnodal sectors; hind wings with 12 ante- 

 nodal and 11 postnodal nervures, the first two postnodals not continuous, triangle 



