250 MR. W. F. KIEBT— A REVISION OP 



papers of great importance ; but Brauer's is the only compendium of the subfamily 

 ■which has hitherto appeared subsequently to Rambur's general work on the Neuro- 

 ptera, published in 1842. The amount of material in the British Museum is very large 

 in this subfemily, including types of nearly all the described genera ; and it was at 

 once obvious that several genera as heretofore employed included two or more natural 

 and easily separable groups, while others, though separated by authors, had less claim 

 to be considered distinct. In the present paper I have attempted to describe all the 

 genera after a uniform system, freely describing both genera and species as new when- 

 ever I considered that I had sufficient material. Nothing makes the study of any 

 group more difficult than the existence of a large number of undescribed (or, worse 

 still, manuscript) species in collections, which will not fit into the arrangement. But 

 although I have in some rare instances ventured to describe well-marked species and 

 even genera from single specimens, I have always refrained from describing any form 

 respecting which my materials appeared to be too scanty to be conveniently utilized 

 at present. I believe that all my new species will prove to be easily recognizable by the 

 characters which I have given, and my descriptions are in most cases taken from a long 

 series of specimens. 



In 1868 Brauer admitted forty genera of Libellulinse, placing them in the following 

 order: — Zyxomma, Tholpnis, Pantala, Tramea, Ehyothemis, DiastatojJS, Palpopleura, 

 Neurothemis, Celithemis, Perithemis, Lexicorhinia, Piplox (= Sympetrum), Mesothemis, 

 Pachydiplax, Erythrodijjlax, Erythemis, Lepthemis, Acisoma, Microtliemis, Brachy- 

 diplax, Nannodiplax, Nannophya, Nannodythemis, Nannothemis, Tetrathenis, Uracis, 

 Lyriothemis, Agrioiioptera, Orthemis, Libelhda, Libella (= Orthetrum), Onychothemis, 

 Diplacina, Pythemis, Macrothemis, Tnthcmis, Bmchythemis, Crocothemis, Macrodi])lax, 

 and Urothemis. 



In the present paper I have characterized 88 genera (of which 40 are new) and 42 

 new species. 



Chakacters of Libellulin.*;. 

 There is a great variety of character in Odonata ; and I have selected the neuration 

 as on the whole the most satisfactory guide. It will therefore be desirable to give a 

 sketch of its principal features, and more briefly to notice one or two other characters 

 of which 1 have made occasional use. But I must first say something of the general 

 characters of the Libellulinse, as distinguished from the other groups of Odonata. 



Subfamily Libellulin^. 

 Eyes large, little if at all expanded behind ; first antenodal nervure of the fore wings 

 not always continuous; nodal sector frequently undulated beyond the middle; hind 

 wings rounded at the anal angle in both sexes ; triangles of the fore and hind wings 

 diflfering in shape. 



