BY R. J. T1LLYARD. 607 



Planipennia. This question will be found discussed under Sec- 

 tion iv. 



(3) The peculiar situation of the forking of K4J.5. -A- little 

 movement of this fork basad would bring it to the main stun 

 of Rs. From this position, R 4 could then become detached 

 from K5, and begin to migrate along the upper branch of Rs, 

 viz. R2+3. A discussion of the origin of pectinate forking of 

 Rs will be found under Sections ii., xv., and xvi. 



(4) The number of branches of Rs and M\_±.. The branches 

 of these veins in this very archaic type are clearly original 

 dichotomies, not additions to an originally simpler venational 

 scheme. Thus the fact that Belmontia possesses more than four 

 branches to both is a serious blow to Comstock's original hypo- 

 thetical type, and prevents us from accepting such a type, with 

 its four-branched Rs and M 1—i as in any way representing the 

 ancestral venational type for the Complex. This conclusion is 

 most strongly supported by the condition of Rs and M 1-4 in 

 the Protomeeoptera (Section x. ), as well as in the great majority 

 of the know r n fossil Mecoptera and Planipennia. The question 

 is fully dealt with under Section ii. 



The great value of the discovery of the fossil Belmontia bes 

 principally in its affording a definite proof of the presence of 

 the extra basal posterior branch of M, viz. M 5| fused with Cuj 

 to form the cubito-median Y-vein, and also in disclosing to us 

 a type from which the Trichoptera and Lepidoptera can most 

 certainly be derived, by way of a common stem-form not yet 

 found in the fossil state, but which must have existed somewhere 

 in Triassic times, though not necessarily in Australia. It also 

 tends to show the Mecoptera in their true form, viz. as a some- 

 what isolated and very early specialisation from the original 

 stem-form of the Complex, and not in any way to be considered 

 as the ancestral Order from which any of the still existing 

 < ►rders have sprung. 



Section x. The Vexation of the Protomecoptera. 



(Text-figs. 57, 64.) 



The Order Protomeeoptera (5) was founded by me for the 

 reception of the remarkable Upper Triassic fossil Archipanorpa 

 magnified Till., from Ipswich, Q. A large portion of both 

 the fore and the hind wings of this fine insect is preserved. As 



