274 
Psyche 
[June-September 
Protereisma americana (Demoulin) 
Figures 6, 7, 9 and 10 
Kukalova americana Demoulin, 1970:6 
The holotype specimen is numbered 631 lab, Museum of Com¬ 
parative Zoology; collected by F. M. Carpenter, locality 15-L, 
Midco insect bed, Noble County, Oklahoma, in 1940 [type desig¬ 
nated by Demoulin by reference to plate 29 and figure 1 in Kuka¬ 
lova, 1969]. This specimen, undoubtedly consisting of the cast 
cuticle of a nymph, shows the general body structure as well as the 
four wing-pads. Its dimensions are as follows: fore wing-pad, 5.5 
mm long, 1.5 mm wide; hind wing, 4.5 mm long, 1.3 mm wide. The 
body is 16 mm long, exclusive of the terminal appendages and 
antennae. A detailed description of this nymph is given in Dr. 
Kukalova’s paper and a photograph of the specimen is included here 
for convenience of reference (figure 6). This is the best and oldest of 
the mayfly nymphs that have been found in any Palaeozoic deposit. 
In addition to the type, there are four other specimens (MCZ 8641- 
8644) showing the gills and other characteristic features; all are 
about 10 mm long, much smaller than the type, and their wing-pads 
are very small or absent. As noted above, isolated wing-pads are 
very numerous in the Midco beds. All have the basic pattern of P. 
americana but of course they may represent more than one species. 
The smallest (MCZ 8638) of these pads is 2.8 mm long and 1 mm 
wide (figure 10A); this shows the venational pattern clearly as well 
as the convexity and concavity of the veins. The largest pad (MCZ 
8636) is 7 mm long and 2.2 mm wide; the cross veins and concave 
veins are more distinct than in the others (figure 10D). Most of the 
wing-pads are 5.5 mm long and about 1.7 mm wide (figures 10B, 
10C). 
There are two aspects of these wing-pads, briefly noted above, 
that are of unusual interest. One is the distinct fluting of the pads, 
even small ones, resulting from the convexity and concavity of the 
developing veins. The fluting seems to be much more pronounced in 
Figure 10. Protereisma americanum (Demoulin). Photographs of wing-pads in 
several stages of development. A, smallest wing-pad found, 2.8 mm long, 1 mm wide, 
showing definite convexities and concavities; MCZ 8638, Permian of Oklahoma. 
Lettering as in figure 9. B, wing-pad 5 mm long, seen under oblique lighting; MCZ 
8639. C, same specimen as shown in B but with flat lighting, showing the intensity of 
the convex veins. D, largest wing-pad found, 7 mm long, the concave veins somewhat 
more distinct; MCZ 8636, Permian of Oklahoma. 
