1976] 
Carpenter & Richardson — Eucaenus ova/is 
239 
of the hind wing (1911, 1920) is either entirely imaginary or based 
in part on his supposed specimen of mazonus (YPM 51), which, 
as noted above, is not even a eucaenid. 
Abdomen. This is of moderate size and not apparently flat- 
tened. The cerci are surprisingly short for a protorthopteron, in 
most of which they are very prominent structures. The small lobes 
on the sides of the more posterior segments (and perhaps all seg- 
ments) resemble comparable structures in other Upper Carbon- 
iferous insects; they were noted by Handhrsch (1911, p. 361) in 
one of the Yale University specimens and are especially clear on 
most segments of the specimen in the Illinois State Museum (type 
of T. mirabile). The ovipositor is short, ordinarily not quite reach- 
ing the end of the abdomen; this is also unusual for a protorthop- 
teron. 
Affinities of the Eucaenidae 
The relationships of the Eucaenidae are difficult to determine, 
mainly because we know so little about other Protorthoptera 
with which they might be compared. About 80% of all described 
Protorthoptera from the Upper Carboniferous are based on fore 
wings alone or even on fragments of the wings. Fortunately, the 
Mazon Creek nodules generally preserve insects with some body 
parts included, although overlapping of the fore and hind wings 
usually obscures the abdomen to some extent, as well as the de- 
tails of the venation. A general survey of the Protorthoptera known 
from the nodules shows that a substantial number of species are 
characterized by a prolongation or some other elaboration of the 
prothorax — certainly a much higher percentage of the known 
species than occurs in other deposits. However, the nature of 
the wing venation indicates that at least some of these prothoracic 
modifications have developed independently within isolated 
lines of evolution. 
There are two families of Protorthoptera from the Francis 
Creek nodules that appear to show similarities to the Eucaenidae 
in both prothoracic structure and venation: Cheliphlebiidae and 
Gerapompidae, Handlirsch consistently placed them close to his 
Eucaenidae. From both of these families the Eucaenidae differ 
in having the costal area much broader and in having SC, R1 and 
the stem of RS close together and parallel. Virtually nothing is 
