BY R. J. TILLYARD. 



363 



changes in the dominant types at each period. We may sum up 

 these tendencies as follows : — 



(1) Tendency towards narrowing of the tegmen. 



(2) Tendency towards reduction of Sc, and invasion of the 

 anterior border of the wing by branches from R. 



(3) A correlated early tendency towards loss of the clear dis- 

 tinction between R x and Rs. 



(4) Tendency for the anal veins to migrate distally from their 

 original endings on the posterior margin of the wing, and to end 

 instead upon the vena dividens. 



Text-fig. 30. 

 Restoration of the tegmen in a. Triassobtatta typica, n.g. et sp., and b. 

 Samaroblatta reticulata, n.g. et sp. Both from Upper Trias of 

 Ipswich, Q. ( x 7£). In b, the intercalated ridges and cross- venation 

 are omitted. 



We are now in a position to study our new Ipswich fossil 

 Cockroaches with advantage. Text-fig. 30 shows the restoration 

 of the tegmina of the two principal genera described in this Part. 



