420 
Psyche 
[September-December 
meets MP and instantly splits into CuA and CuP. As described 
above, all main veins, with the exception of the anal veins, start in 
the hind wing directly and separately from the domed part of the 
axillary plate, as in more advanced Palaeodictyoptera (fig. 4). 
The main difference between the axillary region of the Palaeo- 
dictyoptera and that of the Ephemeroptera is in the attachment of 
the anal veins. In the Palaeodictyoptera, the anal veins probably 
always originated directly from the subcosto-anal plate (figs. 3, 4), 
or the anal plate was closely attached to the cubital plate (fig. 1). 
The anal area in Palaeodictyoptera is often crossed by diverse convex 
ridges, which are sometimes V-shaped ( Homaloneura , Kukalova 
1969), and by transverse grooves (figs. 3, 4A), or the anal veins 
start from a cuticular thickening ( Dunbaria , Kukalova-Peck 1971). 
As pointed out by Wootton (1974, personal communication), these 
structures are in the place of the anal brace of Ephemeroptera. In 
the primitive mayflies, the anal veins start at the anal brace, which is 
basally attached to a small plate, separated from the large axillary 
plate. It seems possible that while the axillary plate originated by 
fusion of the subcosto-cubital plates, the anal plate stayed detached. 
This condition is partially reminiscent of Diaphanopterodea and 
Megasecoptera, as will be shown below. The anal brace in Ephem- 
eroptera is followed, both anteriorly and posteriorly, by two concave 
furrows. By location and, very probably, by function for flight, the 
furrows may be compared with the concave transverse furrow, cross- 
ing the anal area in almost all Palaeodictyoptera (figs. 3, 4A). 
The weak sclerotization of the axillary plate in Ephemeroptera and 
the vanishing of the adjacent stems are probably the changes which 
Fig. 4. Fused subcosto-anal plates of Palaeodictyoptera. A. Dictyop- 
tilus sepultus (Eugereonidae) , enlarged base of the fore wing. B. Steno- 
dictya parisiana ( Dictyoneuridae) , enlarged base of the hind wing. After 
Kukalova, 1970. pa — precostal area; pv — postcostal vein; ScAPl — sub- 
costo-anal plate; tf — transverse furrow. Upper Carboniferous, France. 
