72 
Psyche 
[September 
R3 widely divergent distally, with four rows of cells between them. 
The origin of R4 + 5 from R2 + 3 is not shown in the specimen but it 
is clearly proximal of the level of the nodus. MA and R4 + 5 are 
markedly divergent distally. IA is not recognizable in the part of 
the wing that is preserved. Cross-veins are numerous and are dis- 
tributed as shown in figure ia. 
Holotype: No. 18040, in Museo Argentino de Ciencias Naturales, 
Buenos Aires; collected in the Estratos de Potrerillos, near Agua de 
las Avispas, along the south slope of Cerro Cacheuta, Argentina. 
The formation is of Triassic age (see Romer, i960, for additional 
geological data). The preserved portion of the wing is very clear 
(see plate 9) and the venational convexities and concavities are dis- 
tinct. 
Text-figure IA. Drawing of Triassothemis mendozensis, n. sp., from the 
Triassic of Argentina (holotype). 
Text-figure IB. Drawing of wing fragment associated with above speci- 
men. 
Sc, subcosta : n, nodus ; Rl, radius ; IR2, R2, R3, IR3, R4+ 5, branches 
of radial sector; MA, anterior media; CuP, posterior cubitus; — , 
concave veins; +, convex veins; pt, pterostigma. 
The most striking feature of this wing is the nature and location 
of the nodus. In its form, the nodus is like that of the Archizygoptera 
