*BY R. .7. TILLYARD. 211 



only a change in the shape of the wing, with its consequent 

 alteration in the size and direction of the costal veinlets, and 

 with a correlated specialisation in three parallel main veins, to 

 form the vena triplica (as a kind of backbone or rachis for the 

 widened wing), and a further strengthening of the veinlets by 

 formation of the costal series of cross-veins. 



There is one other point of interest in the venation of Arche- 

 psychops. Comstock, in a recent work (1), has elaborated the 

 theory of the origin of the Planipennia from an older stock with 

 dichotomously branching wing-veins, such as we find in the 

 Mecoptera and Triehoptera. The condition of P44.5 in the new 

 fossil is direct evidence in favour of this, but not in favour of the 

 restriction of the number of dichotomous branches of both Rs 

 and M to four, which Comstock also holds. For it is quite clear 

 that both R 4 and H, 5 , in this fossil, are again dichotomously 

 branched not far from their origins; and quite possibly they may 

 be even branched again, further distad. Thus, we should con- 

 ceive of the ancestral form as having, indeed, truly dichotomously 

 branching sectors of Rs and M, but without any unnecessary 

 limitation of the number of those dichotomies. Such a type is 

 to be seen in the Protornecoj^tera, also from the Ipswich Trias, 

 in which the number of branches of Rs is very large, but all are 

 clearly primitive dichotomies. If we could find the type that 

 gave rise to both Archipanorpa and Archepsychopn, we should 

 most probably have discovered the ancestor of the whole of the 

 Panorooid Orders. 



BIBLIOGRAPHY. 



1. Comstock, J. H., 191S.— 'The Wings of Insects." Comstock Pub- 



lishing Co., Ithaca, N.Y., pp. xviii. ; 430, Plates i.-x., 427 text-figs. 



2. Tillyard, R. J., 1916. — "Mesozoic and Tertiary Insects of Queensland 



and New South Wales." Queensland Geological Survey, Publica- 

 tion No. 253, pp. 1-47, six text-fig;, and nine Plates. 



3. ■ , 1917. — '* Mesozoic insects of Queensland. No.l. Plani- 

 pennia, Triehoptera, and the new Order Protomeooptera. " These 

 Proceedings, xlii., Part 1, pp.175-200, text-figs. 1-7, PI. vii.-ix. 



i. , 1918. — *' Mesozoic Insects of Queensland. No. .">. 



Odonata and Protodonata. " These Proceedings, xliii., Part 3, 

 pp.417-4:u;, text-figs. 11-16, PI. xliv. xlv. 



