190 Ephemeridce from the Tcnasscrim Valley. 



first half of the marginal area : in the same area, a blot of this 

 colour embraces about four cross-veinlets in the middle of the 

 pterostigmatic region ; in the area next below the submarginal 

 area, a spot at the bulla iuchides two cross-veinlets, and another 

 at the apex about three cross-veinlets. 



Imago {dried), 2 .—Body pitch-brown. Femora pitch-brown, 

 with a narrow impure whitish annulation a Utile beyond the 

 middle : tibia; and tarsi brownish white, with the knee whitish ; 

 the fore tibia just below the knee and again at the tip narrowly 

 and faintly annulated with light brown. Setae whitish, rather 

 broadly annulated with blackish at the bases of most of the joints. 

 Ventral lobe of the 9th abdominal segment bifid : the 7th ventral 

 segment unprovided with an egg-valve. Wings vitreous ; the fore 

 wings with pitch-black markings associated with the cross-veinlets. 

 The most conspicuous of these markings are produced by the very 

 broad bordering of the cross-veinlets in the marginal, submarginal, 

 and the adjoining areas, which in places forms quadrangular or 

 subquadrate spots ; some of these in the basal halves of the areas 

 in question, also in the middle of the pterostigmatic region, and 

 again in the two areas which follow that, coalesce into large 

 irregular blotches : posterior to the sector throughout the disk the 

 edging of the cross-veinlets is very narrow, and in many instances 

 only on the exterior side of the veinlet; and here the cross- 

 veinlets are arranged in about ten broken subparallel curved trans- 

 verse series at rather regular intervals. The marginal area of the 

 fore wing contains about three cross-veinlets before the bulla and 

 ten beyond it ; those in the pterostigmatic region are distinct and 

 fairly straight. Length of wing, 5 mm. 



The remaining genera represented in this collection 

 from Tenasserim are : — Baetis by a single $ subim. of 

 small dimensions ; Chirotonetes by a fragmentary <? im- 

 in no way remarkable ; and Heptagciiia by two species, 

 — four J im. and four subim. of one, and a subim. of 

 the other species. Hitherto the genus Potamanthus has 

 been known only as an European and N. American 

 genus, lihoenantlius from the Malay Archipelago, Choro- 

 terpes from Europe and America, Ilagcnulus from the 

 Island of Cuba, and Chirotonetes from America, Japan, 

 Europe, and Sumatra. 



