BY R. J. TILLYARD. 423 



So little of the wing of this fine Dragonfly is preserved, that it 

 would be inadvisable to name it, were it not for the very remark- 

 able characters exhibited by the preserved portion of the wing. 

 It may be stated as a general rule, both for recent and fossil 

 Odonata, that the spaces between C and R, on the one hand, 

 and between R and Mj , on the other, from the level of the ptero- 

 stigma to the apex of the wing, are only filled by a single row of 

 cells. As exceptions to this, we may note the Liassic genus 

 Petrothnnis Handl., in which the distal portion of the space 

 between C and R is filled with three rows of minute cells, and 

 the basal portion of the space between R and Mj carries two 

 ro%\ s of cells near the pterostigma, decreasing to one row only 

 towards the apex; and the very densely-veined Aeschnidiidce, in 

 which the upper of the two spaces in question has only one row 

 of cells, but the lower has two. 



Hence we see that, on this character alone, Perissophlehia 

 stands as the most densely veined of all known Odonata. 



A second character, that is very exceptional in Odonata, is the 

 arrangement and direction of the longitudinal veins lying below 

 Mj. These are so strongly developed that they would appear, at 

 first sight, to be portions of main veins. But a little considera- 

 tion of the position <jf the pterostigma shows us that the pre- 

 served portion of the wing represents only a very small piece of 

 a very large wing. The lowest of the three sectors seen below 

 M] in the fossil is concave, and may very probably be M.^; the 

 other two are almost certainly not l)ranches of M, but intercalated 

 sectors. Of these latter, the upper one, being strongly convex, 

 very probably corresponds with the postnodal sectur, M,a, found 

 in recent Zygoptera and in Petcdura; while that below it might 

 be either a concave supporting sector, or a branch from Mo itself. 

 In any case, the directions of these three veins, two being parallel 

 to one another but converging towards Mj distally, and the third 

 being parallel to Mj, are quite exceptional in the Odonata. 



It is clear then that, in spite of the small amount of the wing 

 preserved, the characters there shown are quite marked enough 

 to warrant the i-ivini; of a name to the fossil. 



