6 PROCEEDINGS OF THE NATIONAL, MUSEUM vol. 79 



median ones with usual dark markings. Anterior wings somewhat 

 shorter than usual, with obliquely truncated apical margin. Color- 

 ing much paler than usual ; the brown reticulation is represented 

 chiefly by a series of short transverse stripes and a few brown spots, 

 partly anastomosing; in the region of the discoidal cell and ptero- 

 stigma a rather large pale spot, and a little nearer to the base is 

 placed a second pale spot between C and Rs ; postcostal area and anal 

 areas also pale. Posterior wings in their ano-jugal region not so 

 dilated as in the remaining species; apical portion a little darker, 

 yellowish. 



Male: Side pieces of the ninth segment broad, but shorter than 

 the tenth segment, upper posterior angle forming a short and narrow 

 triangle. Tenth segment large and of a very composite structure. 

 It forms two side and one median ventral portion ; the last-mentioned 

 part forms two long and thick (if seen from above) processes, di- 

 rected posteriorly; their tips are curved upward, slender and acute. 

 The lateral portions are broad above, as well as laterally, and at their 

 base there is, above, an oval convexity; their apical portions each 

 form three or four slender processes, one ventral, one (or two) 

 lateral, and one dorsal; upper processes longer than the other and 

 directed obliquely upward and inward, with apices acute and cross- 

 ing each other. Preanal appendages long and almost straight. 

 Lower portions of the inferior appendages stick-shaped, but rather 

 short. Upper portions very short; basally they are directed upward, 

 as in other species, but almost immediately divide into two slender 

 processes ; the lower portion is short, directed posteriorly, with acute 

 apex, turned upward; the upper process is longer, rod-shaped, di- 

 rected obliquely upward, with somewhat thickened apical portion. 

 Penis not exserted in our specimens. 



The plates and processes of tenth segment are somewhat polished 

 and brownish ; the inferior appendages are also somewhat brownish. 

 Length of body, 10 to 11 mm. ; expanse, 24 to 26 mm. 



Remarks. — This is a small and peculiar form, differing chiefly by 

 the shape of its wings and by the short, forking upper portion of the 

 inferior appendages. In the configuration of the lateral portions 

 of the ninth segment, however, as well as in the structure of the 

 tenth segment, one may appreciate some resemblance to denticulata 

 and Jongispina of Ulmer. In denticulata the tenth segment is dif- 

 ferentiated into two side, and one median portion, but the side por- 

 tions are slender, the median portion is entire, with but short end 

 processes. In longis'pma the side portions of the tenth segment form 

 similar dorsal processes, crossing each other, but the median portion 

 is also entire and long. In any case siamensis is allied to the group 



