BY R. J. TILLYAKD. 625 



(4) The dichotomic manner of branching of these forks is re- 

 tained, with R.i + 5 forking closer to the base than does R2+3 



(5) Between K 4 and R 5) not far distad from their point of 

 origin, there is a conspicuous wing-spot, probably indicating the 

 presence of a special gland or sense-organ. This is a unique 

 specialisation, and is to be found in all Trichoptera except only 

 the highly specialised and reduced Hgdroptilidae. 



(6) The cubito-median Y-vein is completely formed, exactly 

 on the same lines as in Belmontia. (See Section iii.) 



(7) Fore and hind wings differ in the manner of branching of 

 Mj_ 4 . In the forewing, this vein has four branches, forking 

 dichotomously. In the hind, M 3+4 is always an unbranched 

 vein; so that the total number of branches is reduced to three. 

 (Contrast this with the condition seen in Lepidoptera, in which 

 M 4 fuses distally with Cu la in both icings). 



(8) The cubitus is three-branched, (Jul forking distally as in 

 the Paramecoptera, Megaloptera, and Lepidoptera. 



(9) In the hindwing, 1A fuses with Cu 2 not far from its 

 origin for a short distance, and then diverges from it again. 



(10) In the forewing, the three anal veins are looped up to 

 form a double Y-vein. This specialisation is absent from the 

 hindwing . 



(11) The costal veinlets are reduced to two, viz. the humeral 

 (/?»/) and the distal (dcv) . (In the peculiar genus Perisso- 

 neura, of the family Odontoceridae, the costal space of the fore- 

 wing is widened, and carries a set of from six to eight veinlets. 

 As none of the close allies of this genus show any signs of this 

 peculiarity, I am compelled to regard these veinlets as a special 

 development, like the so-called "false cross-veinlets" or "pseudo- 

 neuria" of the Lasiocampidae in the Order Lepidoptera. In 

 neither case am I able to accept these structures as being truly 

 archaic, and therefore archetypic, characters . ) 



( 12 ) The cross-vein system is considerably reduced, the fol- 

 lowing only being present: — the subhumeral (sh) ; the subcosto- 

 radial (sc-r) ; two inter-radials (ir, ir'), of which one (ir) 

 closes the radial cell (re) distally; the radio-median (r-m) ; the 

 inter-median (im), closing the median cell (mc) distally; the 

 medio-cubital (m-cu) ; the inter-cubital (icu) ; the first inter- 

 anal (m"i) ; in the forewing only, the cubito-anal (cu-a) and the 

 subanal (sa) ; and, in the hindwing only, the second inter-anal 



