on the Ephemeride. 125 
Genus SIPHLURUS,. 
(Ala antica, Pl. III. fig. 2.) 
Baetis, p., Say, 1823 ;| Ephemera, p., Zet. 1840; Pa- 
lingenia, p.» Walk. 1853; Siphlonurus (err.), Etn. 1868. 
Nympha agilis, laminis branchialibus utrinque septem: 
laminarum due priores duplices, czeterze simplices, omnes 
integre. Palpi tri-articulati, superiores proximo articu- 
lorum ceeteris subeequali, et ultimo penultimo breviori; 
inferiores proximo articulorum quoque ceteris subzequali 
et valde depresso, secundo fere obconico apice obliquo, 
et vix tertio longiori. 
_ Super pedes omnes, alis erectis, setisque divergentibus 
subimago stat. 
Imago. Oculi g integri; setz due longe (resi- 
duum intermediz interdum articulatum) ; alee quatuor ; 
tarsi quinque-articulati, proximo articulorum interdum 
tibiz adnato. Forcipis pedes quadri-articulati (nisi arti- 
culus quintus basalis lamini ventrali penultimi segmen- 
torum obtegatur); articuiorum primus largus, secundus 
longissimus. Femina caret ovivalvuli ; neque laminam 
ventralem penultimi segmentorum habet. 
The species inhabit lakes and rivers, in the Palearctic 
and Nearctic Regions. 
From haying omitted to note down the tarsal char- 
acters of all the species examined by me, I am, unfor- 
tunately, unable to adopt Mr. Walsh’s convenient sec- 
tions of the genus ; which are founded upon the structure 
of the tarsus. 
Stphlurus flavidus. 
(Apex abdominis supra, Pl. V. fig. 30.) 
Baetis flavida, Ed. Pict. 1865. 
Imago,v.s.s. 6. “ Oculiceruleo-atri. Corpus fur- 
furosum vel lutescens. Ale vix opace, nervis fuscis ; 
antice juxta bases, et in areis marginali et submargi- 
nali apices versus, pallide flavicantes. Pedes fulvi, 
juncturis fuscis. Abdomen juncturis, et maculis longi- 
tudinalibus apicem versus, fuscis;” subtus maculi U- 
formata in segmento singulo: “ processum depressum 
