BY R. J. TILLVAIID. 



579 



third of the length of the membrane, upon the costal margin. 

 The second branch, R,, is a longer, gracefully curved vein, 

 running below Rj and parallel to the costal margin for most of 



[f*+lS(J ^^^ length, and finally 

 curving up to meet the 

 margin at about two- 

 thirds of the length of 

 the membrane. The last 

 branch, Rs.s, gives off R., 

 close to its base, and im- 

 mediately after divides 

 into R4 and R.,. Ro passes 

 in a gentle curve beneath 

 Ro, and ends up just 

 above the apex of the 

 wing. Rj and Rg meet 

 again (in Dimstania OT\\y) 

 beyond the middle of the 

 membrane, and from there 

 on continue straight to 

 the termen as a single 

 vein R4+5. In Dunstan- 

 Rii^ is a sincrle unbroken vein from its origin to its 



Text-fig. 19.- 



lOpSlS, iV4^5 



termination. 



Returning to the corium of Dunstania (Text-fig. 19 and Plate 

 lix., fig. 15), we can pick up M converging towards R as it ap- 

 proaches the membrane. On the dividing line, it is connected 

 with R by a short, stout cross-vein, forming portion of the 

 dividing line itself. From the swollen root of M upon the 

 dividing line, two branches pass out into the membrane. Of 

 these, the upper, Mj, arches gently upwards, so as to approach 

 close to R3.5, and is connected with R5, just distad from its origin, 

 by a short cross-vein. Thence onward, Mj runs with a slight 

 double-curving to the termen. The lower branch, M2+3, almost 



" Region of node and dividing line in hemelytron of DunManla pnlchra 

 Till., showing the small anterior portion of the coriuin preserved in the 

 fossil; ( X 7'«3). Upper Triassic, Ipswich, Q. 



