72 
Psyche 
[June 
and Lithochrysa, it is much closer to, but still distal to, 
the origin of Rs. In Dictyochrysa, it is barely proximal 
to Rs, while in more advanced forms it progresses toward 
the wing base. The position of this cross-vein in the 
genera herein treated correlates well with the degree to 
which archaic venational features are represented. Un- 
fortunately, Martynov’s illustration of the Jurassic Mesypo- 
chrysa does not include this vein; it would be interesting 
to see if it then occurred still farther out on the wing 
than in Paleochrysa. 
The distad progression of the origin of Rs in the fore 
wing has been discussed by Carpenter. In all three of 
the recent relict genera, as would be expected, Rs originates 
basad of the fork of MP. 
Members of the Jurassic family Mesochrysopidae dem- 
onstrate various degrees of development of the Pseudo- 
media and the Pseudocubitus. Mesypochrysa has a well- 
developed double gradate series, but both branches of 
MP run straight toward the wing margin; there is con- 
sequently no trace of a Psm or a Psc. Mesochrysa , because 
of its apically fused Sc and R, which results in a rather 
myrmeleontiod appearance of the wing apex, is to be 
considered as a specialized side-branch of the chrysopid 
stem. In this genus, however, both branches of MP show 
a tendency to turn posteriad, and a weakly developed 
Psm and Psc are present. The Miocene genera all have 
developed the strong elbow in the branches of MP charac- 
teristic of modern genera; Triplochrysa and Dictyochrysa 
represent a more primitive condition in this respect, the 
branches of MP running posteriad in an even curve. Psm 
and Psc are well developed in the Miocene forms, but 
retain the archaic zig-zagged condition ; Psm in both wings 
runs into the inner gradate series. In Triplochrysa, the 
course of Psm has shifted somewhat toward the margin 
of the wing, and a third, inner, series of gradates occurs. 
Psc remains in a relatively unspecialized condition, merg- 
ing with the outer gradates, and showing fairly strong 
zig-zagging. Psm in more specialized genera has a strong 
tendency to straighten, so that zig-zagging disappears; 
