128 EAST AFRICAN ODONATA—CALVEBT. vol.xviii. 



from tbe liiud augle. A comparisou of flfty-oue specimens of twelve 

 species of Orthetriim now available shows this character not to be gen- 

 eric. Only nine specimens, representing four species, can be said to 

 have the sectors of the triangle distinctly separated at their origin j the 

 remaining forty-two specimens, representing nine species, have the sec- 

 tors more or less united. It is only fair to state, however, that among 

 these latter are some specimens which j)uzzle me to say whether the 

 sectors are to be spoken of as united or separated. Moreover, there 

 are specimens which differ in this particular, in the right and left hind 

 wings; and of at least two species, specimens occur having sectors 

 united and others with the sectors separated. 



The terms "shield-like, marginate," applied to the frons, refer to the 

 demarcation of the anterior face from the sides by a vertical carina on 

 each side, the two carime being united at their lower ends by a hori- 

 zontal carina just above the suture, separating the frons from the uasus. 



ORTHETRUM TRUNCATUM, new species. 



A[((Je. — Vertex dark brown. Frons anteriorly and superiorly dark 

 olive brown, sides yellow, a black line in front of the eyes. Epistoma, 

 lips, and occiput luteous; meutum varying from luteous to black. 

 Nasus sometimes of the same color as the frons, 



Prothorax brownish; posterior lobe as broad as the median lobe, its 

 hind margin slightly emarginate at the middle. 



Dorsum of thorax somewhat luteous, a rather narrow antehumeral 

 black stripe reaching the anterior margin below, and almost the wing 

 bases above; summit of the median carina, edges of antealar sinuses, 

 etc., black; a longitudinal dorsal interalar whitish stripe. Sides red- 

 dish-brown, an oblique pale-yellow stripe immediately behind the first 

 and second lateral sutures, not reaching the bases of the feet below, 

 clearly defined in their lower halves by a narrow circumscribing black 

 stripe; upper halves not circumscribed, ill defined. Behind the second 

 yellow stripe the color of the sides is pale olive. Pectus obscure, lute- 

 ous. Latero-ventral nietathoracic carina of same color as sides in 

 younger males; black in older ones. In older males the colors of the 

 thorax are more or less concealed by pruinose.. 



Feet black, u^jper surface of first femora and first and second tibine 

 luteous in younger males. 



Abdomen viewed from above somewhat dilated at the base; moder- 

 ately narrowed at the base of 4, gradually becoming slightly wider to 

 the apex of 0; thence narrowing very slightly to the apex; viewed 

 from the side, noticeably dilated at the base, but not constricted; 

 pruinose in all the specimens examined. 



Superior appendages black, not as long as the last two segments; 

 viewed from above, straight, only slightly dilated before the apex, 

 which is moderately acute; viewed from the side, each is directed 

 downward, thickest at two-thirds its length, lower side with 7-8 den- 

 ticles; apex hardly upcurved. Inferior appendage two-thirds as long, 



