NO. 1571. DRAGONFLIES OF BURMA AND SIAM— WILLIAMSON. 



315 



example, towaril the condition found in the species described above. 

 Opposed to tliis weak negative evidence of the form of the inferior 

 appendage against referring this specimen to Onychogotuphus, is the 

 very positive evidence for such a relationship shown by the venation 

 which is figured in this paper. Compared with saundersii, which is 

 also figured, there are some very slight, and, I believe, unimportant 

 differences. In Onycliogomphus? species in front wing the first cells 

 included between Cui and Cu, are relatively short in the antero- 

 posterior direction, and the number of cells between these 2 veins 

 at the wing margin is larger in botli front and hind wings. In the 

 hind wing of Oriycfiogompliusf species there is a single row of cells 

 between M^ and Mj^, excepting that the marginal cell is divided. 

 There are also slight difi"erences in the shape of the triangles and 

 subtriangles, and other equally slight differences might be pointed out. 

 (See fig. ^^7.) 



Fig. 37.— Wings of male species of Onychogomphus from Burma 



Genus HETEROGOMPHUS De Selys. 



Seven species have been named in this genus. Foerster regards 

 cochincMnensis De Selys from French Indo-China, and also probably 

 sommeri De Selys from China, as probably races of smitJiii De Selys 

 from Silliet. These three are large species, with the abdomen about 

 55 mm. or more in length and the hind wing 47 to 55 mm. In 

 smitliii abdominal segments 3-7 have the orange more extensive than 

 the black; in cocliincliinensis and sommeri black predominates on 

 3-6 and 7 has about the basal half yellows The character men- 

 tioned hj De Selys for separating sommeri and cocliincliinensis is 

 the coloration of the frons above; in cocliincliinensis the yellow area 

 on the frons above is not divided medianly by black as in sommeri. 

 Foerster has described a male specimen from Tonkui as Hetero- 



