BY R. J. TILLYARD. 



273 



two closely parallel branches, which later on diverge somewhat towards the apex; 

 both of these branches remain simple. M four-branched, its main stem weakly 

 formed; M4 arises obliquely downwards from M3-4 at a point nearer the base 

 than is the forking of M1-2. and shortly after receives from Cui a long branch, 

 m-cu, and then turns to run longitudinally in line with the course of m-cu. Thus 

 between K-j-M and the weak main stem of M above, Ms -4 and the basal piece 

 of M4 distally, and Cui and m-cu below, a closed cell is formed, which we shall 

 call the medio-cubital cell. In this cell lie the remains of an irregular and weak 

 meshwork or archedictj'on, which varies according to the species. Cu with very 

 weak main stem, dividing quite close to the base into Cm and Cu2. Cut gives 

 off first the already mentioned branch m-cu, and then divides into two main 

 branches Cuu and Cuu, both of which reach the wing-margin. Cu2 becomes the 

 vena dividens, separating the clavus from the rest of the wing, and lying in a 

 deep groove close to lA, except at its distal end, where it diverges from lA 

 considerably. Clavus with two distinct, unbranched veins, lA and 2A, the for- 

 mer straight, the latter curved, and arising from the posterior border of the 

 wing near its base. Cross-veins present are only r-m, the elongated m-cu (pos- 

 sibly a true branch of Cui), the irregidar meshwork in the medio-cubital cell, 

 and sometimes cu-a. Hindming: Rs arising at from one-fourth to one-third along 

 the wing, unbranched, or perhaps sometimes branched distally. M only three- 

 branched. Cui two-branched ; Cu2 a weak vein arising far along Cu, and becoming 

 obsolete long before reaching the wing-margin. (Anal veins not well preserved, 

 two or possibly three). Cross-veins present are only r-m, m-cu (short in this 

 wing) and cii-a, with sometimes sc-r and another r-m situated more basally be- 

 tween the main stems of R and M. 



Genotype, Mesngereon neuropunetatum Till. (Upper Triassic, Ipswich, 



Q)- 



R. 



— Sc 



Text-fig. 65. — Mesogereon neuropunetatum TiUyard. Details of venation 

 in forewing. (x 6J) . 



Mesogereon neuropunctatum Till. (PI. xxi.. fig. 24; Text-fig. 65.) 



Tillyard, Q'land Geol. Surv., Pub. 253, p. 34. Plate i.. Figs. 1, 2. 



A fragment of a forewing, measuring 23 mm. greatest length by 17 mm. 

 greatest breadth. Studied in the light of the new material, this fragment is found 

 to consist of a small portion of a very large wing, probably between 50 and 60 



