nilROPTERAN NOTES 



23 



Rh. stheno is at onci^ distinguished from Rh. horneensii^ and 

 Rli. rouxi Ijy the following characters: — 



(1) By the very strongly and abruptly projecting nasal swel- 

 lings; compare the skull of Rh. stheno in side view (Proc. Zool. 

 Soc. London I90o II. pi. III. fig. 8 a) with that of Rh. borneensis 

 { ibid. tig. o 1)) and Rh. rouxi (ibid. fig. 9 c) ; in this j)()int 

 Rh. stheno is unique among the eastern species of the Rh. simplex 

 group. 



(2) By some interesting {)eculiarities in the wing-structure, as 

 shown by the subjoined table of wing-indices: the wing-structure 

 of Rh. borneensis, it will be observed, is in all important respects 

 similar to that of Rh. rouxi, with the only exception that 

 RJi. rouxi has proportionally longer metacarpals; in Rh. stheno. 

 however, the following modifications have taken place: — first, 

 tlie third and fourth metacarpals are somewhat shortened; second, 

 all the proximal phalanges are shortened, especially the first 

 phalanx of the fourth digit: in Rli. borneensis and rouxi 

 this phalanx is much more than, in Rh. stheno almost precisely 

 equal to , one fourth the length of the metacarpal ; third , the 

 second phalanx of the third digit is noticealily lengthened: in 

 Rh. borneensis and rouxi it averages decidedly less, in Rli. stheno 

 more, than I -^ the length of the first phalanx. 



(3) By the very sliort tail: considerably shorter than the lower 

 leg, whereas in Rh. borneensis and rouxi it is longer than or 

 equal to the lower leg. 



Rh. stheno has two rather close relatives in South Africa, 

 viz. Rli. simulator, K. And., and Rii. denti, Thos. 



Wing-indices of Rliinoloplius borneensis, rouxi, and stheno. 



