1976] 
Carpenter & Richardson — Eucaenus ovalis 
235 
of the fossils studied, with the exception of the few veins shown 
in broken lines. 
Discussion of the Structure of Eucaenus ovalis 
Head. The head of ovalis was presumably opisthognathous 
and it is so preserved in several specimens; however, it is also 
shown in a prognathous position in a few fossils, notably Greene 
G75. There seems to be nothing unusual about the antennae or 
compound eyes, but the long palpi (presumed to be the maxillary 
pair) are remarkable. They are exceptionally clear in two speci- 
mens (Greene G75 and PE 20790). Such long palpi are very un- 
usual among existing Pterygota. In the orthopteroids, compara- 
ble palpi occur in a few species of Gryllacridoidea, especially of 
the family Stenopalmatidae; so far as known these are wingless 
and live in rotting wood or are subterranean. 
Thorax. The prothorax is the most conspicuous and peculiar 
part of the thorax. Between the head and the pronotal shield 
there appears to be a separate, strongly sclerotized segment, which 
we have interpreted simply as the anterior part of the prothorax. 
This could conceivably be a sclerotized cervical region, although 
we are not aware of any such structure in existing insects. It is 
worthy of note in this connection that a considerable number of 
Upper Carboniferous Protorthoptera, not especially close to 
the Eucaenidae, have similar sclerotized regions, although they 
have not been discussed in the literature. 
The pronotal shield shows considerable variation in shape 
among the specimens studied but a significant part of this diver- 
sity is apparently due to the nature of the preservation of the in- 
dividual specimens. In some instances, the pronotum is obviously 
different in shape in the counterparts of the same fossil. Hand- 
lirsch stated (1911) that the pronotum of the male was compara- 
tively smaller than that of the female, but we have found no relia- 
ble evidence for that conclusion. 
Wings. The fore wings are distinctly oval in shape; combined 
with the form of the costal area, this is one of the major charac- 
teristics of the insect. The number of costal veinlets is quite varia- 
ble, as noted above; the costal area of the wings in figures 2 and 
3 is based on the Greene specimen G75, which has about the maxi- 
mum number. The veinlets presumably continue for the full length 
of the costal area, though the distal part of the area is not satis- 
