EEY. A. E. EATON OX EECEXT EPHEMEEID^ OE :NL\TFLIES. 245 



surface of the head. Pronotaui of 2 somewhat eordately excised behind; the reflexed 

 lobes rounded. 



Sv.bimago. — Wings yellowish or gi-eyish in tint ; neuration opaque, not edged with 

 greyish. 



Nymph intermediate in character between Epeorus and Wiithrogenn. — Abdominal 

 tracheal branchiae disposed as in the latter genus, with short sparse fasciculate fibrils ; 

 laminae of the ^foremost pair very large, transverse, narrowly subreniform with the sinus 

 eccentric, in mutual contact at their inner extremities beneath the metasternum ; laminae 

 of the intermediate pairs obliquely reclinate at the sides, lessening successively in breadth 

 from the foremost, and also in length (but in both directions) from the third and fourth 

 pairs, each of them oblique, more or less broadly ovate and subacute, with the outer 

 or inferior margin thickened and ciliate ; laminae of the hindermost pair obliquely 

 conduplicate and incurved so as to meet at the tips when deflected beneath the pen- 

 ultimate segment : branchial tracheae distinct, pinnately branched, but largely deficient 

 towards the thickened portion of the lamina (which part is broader in Iron than in 

 Epeorus), and both coarser and sparser than in the preceding genus. Pronotum 

 transverse, short : the hind margin uneven ; the lateral margins undilated and mutually 

 subparallel. The markings on the coloured side of the femora comprise two groups of 

 longitudinal streaks with a rounded spot interposed between them, somewhat as in 

 Epeorus ; but in Iron this spot is isolated. Caudal setse and mouth-parts similar to those- 

 of Epeorus. 



Type. T. longimanus, sp. nov. 



Distribution. Xorth America, and (undescribed species in M^'Lach. Mus.) on Irazu in 

 Costa Rica. 



Etymology, e'lpw, a dissembler. 



The identification of the nymph rests upon specimens from "Washington Territory in 

 Mus. Comp. Zool. Cambridge, !Mass., communicated by Dr. Hagen, representing subimago 

 and nymph, viz. : — 1 d and 1 $ subim. registered " Wenas V., W. T., Pressy's 7. vii. 

 1882," and 3 nymphs registered " Klikitat V., W. T., Thorpe's 10. vii. 1882, S. Henshaw." 



Irox LOXGiMA>'rs, sp. nov. Plates XXIII. & XXIV. 44 (wings and legs), LXY. 2 

 (genitalia). 



Epeorus (Colorado sp.), ! Etn., Ent. IMo. Mag. xviii. 26 (1881). — E. longimanus, ! id., in the writing 

 of PI. XXIII. of this monograph (1883) . 



Iron longimanus, lEtn., in the writing of PL XXIV. of this monograph (1883). 



Imago {dried) 6 . — Notum either light yellowish ochre, or a light reddish-brown ochre. 

 Dorsum of abdominal segments 2-9 tinged extensively with Kght brownish [sometimes 

 light bistre, sometimes Vandyke], and in segments 2-7 exhibiting slightly depressed 

 spaces translucent and deficient in colouring, viz. : — on each side of the segment an 

 elongate ellipsoidal spot near the plem-ae, and a narrow space extending from spot to 

 spot across the base ; there is also, as frequently in EphemeridcB, a small obovate or 

 elongate pale spot on each side of the dark tract of the dorsal vessel ; segments 9 and 10 

 ire sometimes light-brown ochre, with a dark line down the middle : the pleurae are of a 



SECOND SERIES. — ZOOLOGY, VOL. III. 33 



