1895. PROCEEDINGS OF THE NATIONAL MUSEUM. 129 



luteous, edged with black, broad; apex emarginate when viewed from 

 below, ending in two upcurved denticles which do not reach the last 

 denticle on the superiors. 



Genitalia of 2 moderately prominent. Anterior lamina slightly more 

 prominent than hamnle or genital lobe, its apex slightly emarginate in 

 the middle. Hamule bitid, branches widely divergent; internal branch 

 when viewed from the side considerably thicker than the anterior 

 lamina, its apex almost truncate, somewhat hooked on its outer side, 

 a little less prominent than the anterior lamina; external branch much 

 shorter, lying against the ventral margin of 2; apex rounded. Genital 

 lobe rather broad, about as prominent as, or less so than, the internal 

 hamular branch. 



Wings hyaline, somewhat smoky; reticulation black, costa luteous 

 anteriorly. Hind wings only with a small yellowish cloud alongside 

 the membranule, never extending outward 

 farther than a single cell. Pterostigma 4-5 

 times as long as wide; bright ocJier yellow. 

 Membranule cinereous, whitish at the base 

 and along tlie alar side. Front wings with 

 11-14 antecubitals, 8-11 postcubitals, one 

 hypertrigonal, one median cross vein, triangle Fig. 6. 



with one cross vein, three rows of posttriangu- orthetrum trunc.\tum. 

 lar cells, internal triangle of three cells. Hind 



wings with 9-10 antecubitals, 9-12 postcubitals, no hyj)ertrigonals; 

 triangle free, median cross vein placed nearer the base than the first 

 antecubital; two rows of posttriangular cells increasing, no internal 

 triangle; sectors of the triangle united at their origins.' 



The female is unknown to me. 



Measurements. — Total length, 40.5-43 mm. Abdomen, 27-30. Front 

 wing, 30-33.5. Hind wing, 29-32.5. Pterostigma, 3-3.25. Width of 

 abdomen at base, 2.5; at base of 4, 1.5; at apex of 6, 2. 



Locality. — Six males in the ISTational Museum collection, from Kili- 

 manjaro. 



At first, 1 had referred these specimens to 0. chrysostigma, Burmeister 

 {(). harbara, Selys). Mr. W. F. Kirby has kindly compared a tracing of 

 the accompanying figure of the genitalia of O. truncatum with a male 

 O. chrysostigma in tlie British Museum, with the result that the latter 

 has the anterior lamina very short and slender (much less prominent than 

 the hamule and less than tlie genital lobe); the hamule decidedly 

 more i)rominent tliaii the genital lobe, and in general "the genitalia 

 agree with M. Albarda's ^ description as far as it goes." There are 



'Variations in reticnlation in the front wings: One male has no liypertrigonals in 

 left wing; another has two cross veins in the right wing; a third, has the internal 

 triangle of two cells in the l«ft wing. In the hind wings, the posttriangular series 

 soiuetiraes commences with throe cells. 



2Cf. Albarda, Ann. Soc. Kiit. Belg., XXXI, p. li), 1887. 



Proc. X. M. 95 9 



