on the Ephemeride: ¢@ 
Potamanthus Ferreri. 
P. Ferreri, Pict. 1843-5. 
Imago, ¢. ‘Thorax pallide furfurosus, macula dorsali 
pone prothoracem fuscé. Al vitrine, nervis pallidis- 
_sime flavescentibus, et pluribus transversalium indiscretis. 
Pedum antici pallide fusci, femoribus coxisque saturatio- 
ribus, et juncturis flavis; posteriores pallide furfurosi, 
invaril. Abdominis dorsum fuscum, latera versus fulvum, 
macula media trigonali super singula segmenta; venter 
fulvus. Sete et forceps pallide flavee.” 
Long. corp. ¢ 13, set. 18, exp. al. 30 mm. 
Hab.—Turin (Pict.). 
Genus LEprorpHLEBiA. 
(Ala antica, Pl. IT. fig. 2a.) 
Ephemera, p., Lin. 1746. Baetis, p., Burm. 1839. 
Leptophlebia, p., Westw. 1840. Potamanthus, p., Pict. 
1843-5. Palingenia, p., Walk. 1853. Leptophlebia (re- 
stricted) , Htn. 1868. 
Imago. Ale quatuor. Setarum media est longa vel 
abbreviata. Oculi maris sub-partiti. 
It is with very great hesitation that I venture provi- 
sionally to retain in this genus the majority of the species 
placed in it. Ignorance of their preparatory stages of 
development compels one to class them all together, for 
the present. The group to which L. fusca belongs seems 
at first sight to be clearly distinct from the rest; but the 
nymph of L. fusca resembles that figured by Professor 
Pictet as the nymph of ZL. cincta; and besides this, in 
the closely allied genus Daetis, it is found that considerable 
differences in the form and neuration of the posterior 
wings of species are compatible with their being in the 
same genus: therefore L. fusca, in spite of appearances, 
can hardly be separated from the group of which LZ. mar- 
ginata is the type, with safety. On the other hand, the 
differences between the group last mentioned, and that 
of which JL. eupida is the type, are, upon the whole, 
equivalent to those between Ephemera and Hezxagenia ; 
therefore it may be a mistake to consider them as sections 
merely of one genus. When the nymphs are known, all 
doubts will be set at rest; but not until then. Most likely 
