254 
Psyche 
[September 
the may-flies is really MP, and their MA is reduced and 
has completely vanished. Cu is divided into two simple 
branches, in which one can also see CuA and CuP of the 
Palseodictyoptera. Then come the anal veins; the long A 4 
with its branches, and another long one, A 2 or A 3 , with 
its branches. The character of the cross-veins Ss the 
same as in Ephemerids. As already mentioned the fore 
and hind wings in the may-flies of the Permian were alike, 
their shapes quite resembling those of the Dictyoneurid 
wings; but in all that is known to us, MA was already 
missing. The branching of RS is also very much like that 
of Triplosoba and of the contemporary Ephemerids, while 
here also (Protecha Sell., Protereisma Sell.) RS 4 arises 
near RS 5 , and the rest of the branches form the distal 
group. The branches RS 4 and RS 2 represent “inserted 
sectors” as in the recent Ephemerids. 
According to the interpretation of Sellards and Hand- 
lirsch, Cu is divided into two branches at the very base; 
the anterior of these also divides into two side branchlets 
and a middle “inserted” one (in Protechma) ; and the pos- 
terior branch gives rise to two small branches directed 
posteriorly. The anal region is badly preserved. On ac- 
count of this poorly preserved anal region it is difficult 
to say how to regard the two branches of the cubitus, 
whether they correspond to CuA and CuP of the Palseo- 
dictyoptera or whether there is another interpretation pos- 
sible. Incidentally, the anterior branch with its branch- 
lets is very much like the cubitus of Siphluridse, Ecdyuridse 
or Leptophlebiidse. 
The fore wings of the recent may-flies, because of the 
division of labor between the wings (all work of production 
of strokes and stroking the air being transferred to the 
fore wings), increased their dimensions and took the shape 
of elongate triangles, as in many Papilionidse ; as to the 
hind wings, where they are developed best of all — in 
Ephemeroidea and Pleptagenioidea — they are of an oval 
or round shape as in many Rhopalocera, and in other may- 
flies — in Bsetidse, Ephemerellidae, and Csenidse — they are 
subject to greatest reduction. The fore wings, substituting 
in these groups for the disappearing hind ones, grow wider 
in the cubital and anal region and take a shape which 
