SYNOPSIS OF THE BRITISH EPHEMERID.E. 23 



wings paler; egg-valve short, broad, with rounded 

 corners. 

 Length of the body ^ 61, $ 7 lines ; expansion of the 



wings (? 17 1, 2 I6h ; setae $ 22 J, $ 14 lines. 

 Sub-imago dull brown-grey ; thorax yellowish in the 

 middle ; caudal filaments and legs brown-grey ; wings 

 grey, the transverse veins generally margined with 

 darker ; the marginal field not darker. 

 The description is made from Prussian specimens, which 

 have been compared with the types of the sub-imago. I 

 have English specimens before me. 



Habitat near London ; Ambleside, June ; scarce. 



2. B. LUTEA, Stephens; JEpk. lufea, Stephens, 57, 5, 

 $ imago ; Eph. marginata, Stephens, 57, 6, $ imago. 



Imago. Dark luteous ; on the hinder part of the head 

 near the eyes is a triangular black spot ; the abdominal 

 segments with a dark-brown band at the tips ; caudal 

 filaments yellow, the joints annulated with black ; 

 anal forceps and legs yellow, the anterior legs hardly 

 darker; wings hyaline; costa pale yellow, with par- 

 tially darker black-brown transverse veins ; apex of 

 the marginal field with straight transverse veins : penis 

 double, straight, cylindric, the apex cup-shaped. 



Female similarly coloured throughout, but paler ; egg- 

 valve oval ; ventral plate of the last segment incised 

 in the middle. 



Length of the body ^ 3i, 2 4 fines ; expansion of the 

 wings $ \l\, 2 14 lines; sets ^14, 2 85 lines. 



Sub-imago coloured quite similarly to the imago, but 

 duller, with a greyish tinge ; easily recognised by the 

 black-brown transverse veins of the costa. 



Habitat near London, in June. 



