406 Records of the Indian Museum. [Vol. XXIV, 



sixth the distal third. In addition these segments have each an 

 obscure darker longitudinal mark occupying about the middle 

 of the segment. The basal two-thirds of the seventh segment are 

 yellow, the apical third is black. Segments 8, 9 black, 10 golden 

 brown margined apically with black, and with black marking on 

 either side of the middle line dorsally. 



Anal appendages yellow, very like those figured for 0. geometri- 

 cus in the monograph. Upper pair as long as segments 9 and 10 of 

 abdomen, curved downwards, cylindrical and tapering to a point. 

 Branches of lower pair closely approximated, rather abruptly 

 curved upwards at the commencement of their apical third, trun- 

 cate at their apices, rather shorter than the upper pair ; and each 

 carrying a dorsal tubercle at the end of the basal third of their 

 length. 



Length of abdomen of & 35 + 3 mm., of hinder-wing 305 mm. 



The species of this section of the genus may be distinguished 

 as below. 



A. Narrow complete black band on second lateral 

 suture only, position of first lateral suture unmarked. 

 Segments 3-6 with apical two-thirds yellow or 



brown, distal third black ... ... ... 0, aureus, sp. now 



CJaro Hills, Assam. 



B. Black bands marking the position of both lateral 

 sutures of synthorax. 



1. Lower anal appendage of male black, upper 



pair tipped with black ... ... 0. saundersi Selys. 



Burma, Sumatra 

 (Malay Peninsula?). 



2. Anal appendages of male entirely orange ... 0. geometricus Selys. 



Java. 



C. Black bands marking the position of lateral su- 

 tures confluent over the metcpisternite ... 0. saundersi Williamson 



(nee Selys?). Burma. 



There is a male specimen of a species of this group in the 

 British Museum from Tonkin ; I have not been able to identify it ; 

 but on casual inspection it would appear to be 0. geometricus. I 

 have also had the opportunity of examining a specimen from Su- 

 matra identified by N. H. Campion, and of discussing it with him. 



Section IV, biforceps. 



Colouring largely black, dorsal bands of synthorax confluent 

 or not with mesothoracic collar, antehumeral stripe present or 

 absent. Dilatation of apical end of abdomen begins abruptly at 

 base of eighth segment, the apical half of the seventh being scarcely 



enlarged. The dilata- 

 tion attains its maxi- 

 mum at the middle of 

 the eighth segment. 

 Lower anal appendage 



Kio. i8.— Apex of abdomen of Onychogomphus of male longer than 

 biforceps, Selys, 3, seen from above. upper pair ; its branches 



separated at their ori- 

 gin by a circular space. The branches project beyond the end of 



