1958 ] Adams — Protoperlaria and Endopterygota 121 
veins only. There is a decrease in size toward the 
base of the wing. 
In attempting to differentiate between the setae on the 
veins and those on the membrane, Tillyard greatly over- 
emphasized in his discussion the larger size of the setae 
on the costa and other veins. While it is true that the 
costal setae are very slightly larger than those of the mem- 
brane, much of the apparent size difference is illusory; 
in the fossil the setae of the wing membrane, seen against 
a colorless background, look brown, while those on the 
veins, seen against a brown background, look black, and 
therefore heavier. 
Even though some size difference exists, this is not in 
itself sufficient reason for interpreting the hairs on the 
veins as macrotrichia, and those on the membrane as mi- 
crotrichia, for in SiaUs there is a similar size difference. 
Furthermore, the microtrichia of Sialis (indicated by 
stippling in Figure 7, and shown in more detail in Figure 
6) are very small, about the same size as the grain of the 
matrix in which are imbedded the fossils. Even were 
similar microtrichia present in Lemmatophora, as was al- 
most certainly the case, they would therefore be obscured 
by the grain of the rock. 
Tillyard’s reluctance to recognize the macrotrichia on 
the wing membrane of Lemmatophora as such was probably 
due to an impression that macrotrichia do not occur in 
this location among the Exopterygota. While this is gen- 
erally true, there is at least one exception. Since the Ple- 
coptera are considered to be descended from the Proto- 
perlaria, an examination was made of the wing surface 
of a representative of this order, Pteronarcys calif ornica 
Newport. In this insect, prominent microtrichia are scat- 
tered over the entire wing. Small macrotrichia are sparsely 
distributed on the veins of the fore wing. But on the 
anal fan of the hind wing near the margin, large macro- 
trichia occur not only on the veins, but also on the wing 
membrane (Fig. 5). 
From the above evidence, it seems reasonable to conclude 
that macrotrichia were present on both the veins and the 
