150 Transactions. — Zoology. 



"Deleatidium lillii (Eaton). 



" Subimago (in fluid). — Wings uniformly light-grey, with 

 opaque neuration. Setae grey, their joinings towards their 

 tips evenly defined. 



" Imago (dried). — $. Body pitch-brown, the thorax po- 

 lished above. Femora and fore tibiae raw umber-brown, fore 

 tarsus and hinder tibiae lighter in tint, hinder tarsi some- 

 what of a sepia-grey throughout. Wings vitreous, with pitch- 

 black neuration, except in the fore wing, the finer cross- 

 veinlets of the marginal and submarginal areas that precede 

 the pterostigmatic region (which are deficient in colouring) , 

 and the roots of the stronger nervures interior to the humeral 

 cross-vein, which are raw umber-brown ; the membrane at 

 the extreme roots is almost imperceptibly tinted raw-umber 

 or greenish. In the marginal area of the fore wing, before the 

 bulla, are usually about 6 faint cross-veinlets, and beyond that 

 2-4 faint and 8-11 stronger veinlets, all simple. Setae light 

 sepia-grey with blackish joinings, of which some in the basal 

 quarter are alternately distinct and faint. In the abdomen, 

 segments 3-6 are sometimes transparent and whitish to a 

 variable exteut at the base. 



" $ . Very like the $ , but the colouring at the fore- wing 

 roots, interior to the humeral cross-vein, is rather darker in 

 tint. The marginal area of the fore wing contains about 

 3-5 faint cross-veinlets before the bulla, and 2 faint and 

 13 stronger beyond that, all simple. Ventral lobe of the 9th 

 abdominal segment slightly (not deeply) emarginate, with 

 acute points. 



"Length of body, 8-9 mm.; wing, 12 mm.; setae, (Jim., 

 51 mm." 



a. Dorsal view. 



b. Ventral view. 



c, d, e. First, second, and third legs 

 /. Second maxillae and labium 



DESCRIPTION OF PLATE VII. 

 Ephemerid Nymph (unknown). 



g. Right mandible. 



h. First maxilla, right. 

 k. Labrum. 

 t b., 1-7. Tracheal branchiae. 



