BY R. J. TILLYARD. 183 



upon it. Apparentl}^ a small extra apical forking of Rg in Af.2. 

 Beyond dc, no extra cross-vein between l^. and R4. No cross- 

 veins in Af.2; the wing-point (sp) not clearly shown, but ap- 

 parently present just below the distal side of dc. Subdiscoidal 

 cell {sdr) present, shaped as in Mesopsyche, but considerably 

 broader. Median cell {rtic) present, of more regular shape 

 than in Metioiisyche. Af.4 strongly sessile upon it. Af.3 

 either slightly sessile, or just arising from its upper distal angle 

 (as in Mesopsyche). Af.3 divided into two cells by an extra 

 cross-vein joining Mj and Mo. Thyridium (t) placed directly 

 under the main forking of Rs (as in Mesopsyche). Thyridium- 

 cell (tc) present, elongated, pentagonal, closed off distally by a 

 strong cross-vein from M4 to the weakly zig-zagged Cuj. A 

 second cross-vein, parallel to this, separates off a post-thyridial 

 cell (ptc) between M4 and Cui. Only the distal portion of Cu is 

 preserved; apparently Cu., fuses with lA not far from the wing- 

 border, and the very irregularly formed Af.5 is divided into two 

 cells by means of a cross-vein dropped from Cuj obliquely on to 

 1A + Cu2 almost at the wing-margin. 



Genotype, 7'riassopsyche dunstani, n.sp. 



Though not so well preserved as the wing of Mesopsyche, 3^et 

 this fossil shows most of the details necessary for a reconstruc- 

 tion to be possible. Several of the cross- veins are not com- 

 pletely preserved (see Plate vii., fig. 2). There is a roughly 

 raised linear mark extending between M-M4 and Cu-Cu,, which 

 at first sight looks as if it might be covering a main vein. Fortu- 

 nately, as Cuj is always a well-marked convex vein, it was pos- 

 sible to determine tliis question definitely. For, in the fossil, 

 the vein marked Cuj is definitely convex, and hence there can 

 be no main vein between it and M-M4. The vein marked lA is 

 so determined because, at the point where it is broken off" proxi- 

 mally in the fossil, it is definitely diverginy proximad from Cu. 

 Had it been converging, it would have been determined as Cug, 

 and the vein marked Cu.^ in the figures would have been con- 

 sidered a specialised cross-vein. 



In Text-fig. 3, I have attempted the restoration of this fine 

 wing, which must be reckoned among the largest Trichopterous 



