EEV. A. E. EATON ON RECENT EPHEMEEID.E OE MAYFLIES. 219 



the place correspondiug with that of the praeterminal band in other species ; tibiae and 

 some part of the tarsi basewards rather lighter than the femora, but the remainder of 

 the tarsi about as dark as the femora. Wings vitreous ; nenration in opaque view 

 pitch-black, with the wing-roots and the bases of the longitudinal nervures very light 

 bistre-brown in both wings, and also with the costa of the hind wing to a large extent 

 pale. 



? . Very similar. The ventral stripes in segments 2-6 combine to form wider curves 

 tlian in the 6 , and the innermost pairs of dark dots stand apart from the stripes ; 

 segment 7 has a pitch-black triangular stripe on each side from the base, an ochraceoiis 

 depression in the midst, and a broad dark-coloured ovivalvular border ; segment 8 is 

 bright yellow-ochreous in the midst, and is traversed by a blackish longitudinal stripe on 

 each side, which is continued through the following segments to the base of the seta ; 

 segment 9 is edged very narrowly at the sides with yellowish, and traversed longitudinally 

 by an abbreviated median yellowish cuneiform streak tapering forwards from the base of 

 the lobe ; the lobe itself is largely occupied by an ochraceous rhomboidal spot truncate 

 anteriorly at the base of the lobe so as to be reduced to the form of an irregular pentagon, 

 and its anterior lateral margins are narrowly ochraceons. Fore legs intense raw-umber. 

 Setae whitish sepia-grey, sometimes dark near the roots ; the joinings for the most part 

 blackish. Length of body, d 11-12, ? 13; wing, d 12-14., 2 16; setae, 6 im. 16-22, 

 2 im. 22 mm. 



Hab. Colorado and Washington Territory (M°Lach. Mus.) ; also (in Mixs. Comp. Zool. 

 Cambridge, Mass.) Truckee, Nev. (Crotch, June 10), between EUes and Humboldt, Nev. 

 (S. Henshaw, June 10), Bridger Basin, Wy. (Garman), and Manitou, Col. (Morrison). 

 The description given above is based mainly upon specimens from Colorado in M^Lach. 

 Mus. Those from Washington Ter. have the forceps-basis uniformly bistre-brown ; and 

 their hinder legs may be almost imperceptibly of a darker shade than those of the typical 

 form. This last difference is slight enough to be attributable to fortuitous causes. In 

 accordance with prevalent usage, the name brimnea is restricted to the <s imago described 

 by Hagen in 1875, which is a BJiithrogena ; but in that genus also it will rank as a 

 synonym. 



SiPHLURUS ALTERNATIJS, Say. 



X Bcietis alternata, Say, Godman's West. Quart. Rep. ii. 304. (1824.) ; Le Conte, Comi)lete Writings of 

 r. Say, i. 204 (1859) ; Hag., Smithsoo. Miscell. CoU. (1801), Syiiopt. Neiu-opt. N. Am. 49 ; Walsh, 

 Proc. Acad. Nat. Sc. Philad. (18G2), 369 ; Hag., Proc. Ent. Soc. Pliilad. ii. 109 (1863) ; Walsb, o^j. cit. 

 189 (1863).— t B. II annulata, ! Walk., List of Neuropt. Ins. iu Brit. Mus. part iii. 567 (1853) ; Hag., 

 3mitlison. Miscell. Coll. (1861), Synop. Neuropt. N. Am. 48.— ± B. Xfemorata, Provauelicr, Naturl. 

 :anad. viii. 267 (1876) ; id., Fn. Ent. d. Canad. ii. fase. i. ^3 (1877). 



Siphlurus annulatus, ! Etn., Tran.s. Ent. Soc. London (1871), 127, pi. vi. 4, 4:a [forceps and ventral 

 narkings]. — S. alternatus, id., op. cit. 129 (1871). — S.alternans [misprint in corrections for aliernatus'], 

 ?rovanclier, Fn. Ent. d. Canad. ii. fase. i. 82 ^ (1877). 



Stibimago. — Wings furaose, with coarser and more distiuct neuration than those of the 

 mago : nem-ation and membrane pale greenish at the tips of the hind wings (Walsh). 



29* 



