306 
Psyche 
[December 
larger and to have a dorsal ridge running along the lateral edges of 
the notum and between the meso- and metathoracic segments; the 
metathorax has a similar ridge, which is indented posteriorly. How- 
ever, not much weight can be given to these vaguely preserved details. 
There are no clearly preserved legs; this is most unfortunate, since 
they might show some adaptations for aquatic or terrestrial environ- 
ments. 4 It is pertinent to note that in the adults of Mischoptera only 
the fore pair are known, these being very short and curved under the 
front of the head (Plate 26). abdomen. This is long and consists of 
ten nearly homonomous segments and a shorter, rounded eleventh seg- 
ment. The hind margins of all of the abdominal tergites, excepting 
the last two, bear a row of seven stout spines, including the two that 
appear to be continuous with the lateral edges of the tergites. These 
spines, which are best studied with the aid of alcohol or glycerin and 
which can clearly be seen in the photograph (Plate 27, fig. 1 ), are sim- 
ilar to those in the adult Mischoptera but somewhat larger. The ab- 
dominal segments also show a series of longitudinal lines somewhat 
removed from the sides; they are preserved on only one side in the 
obverse but on both sides in the reverse. They are possibly the ventral 
margins of tergites, their impressions resulting from the flattening of 
the abdomen during preservation, or possibly lamellae, like those in 
mayfly nymphs. However, there is some doubt in our minds about 
the correct interpretation of the structures along the sides of the 
abdomen. The cerci, which are covered with hairs and are an- 
nulate, are preserved only for a short distance but they were clearly 
well developed and probably about as long as those of the adults. 
Superimposed on the tenth abdominal segment is the impression of 
two small projections; their identity is by no means clear but they 
probably represent part of developing genital structures. The sim- 
ilarities between douglassi and adult Mischoptera are obvious. The 
most striking one, of course, is the nature of the thoracic spines, but 
there are in addition the antennal segmentation, the tergal spines of 
the abdomen, and the pattern of wing venation. The only distinctive 
difference is the lack of actual contact between Rs and MA in the 
nymph, but this is perhaps due to the immature state of the wing. 
Two additional specimens of megasecopterous nymphs in the iron- 
stone nodules have also been examined ; both were collected near the 
Will-Kankakee County line (Peabody Coal Company Pit 11). One 
of these, No. 41 1 in the collection of Mr. Jerry Herdina, is a whole 
4 One metathoracic leg is vaguely preserved in the Herdina specimen 
(No. H411). 
