BY R. J. TILLYARD. 33 



only found very much further north, the former extending from 

 Papua to Cairns, the latter from Cape York to Townsville. The 

 resulting contour exhibits a typical fctoyenic arrangement, the 

 zoocentre containing five species and lying so as just to intrude 

 into the northern part of Australia. 



Other genera of Odonata exhibiting a contour similar to this 

 in general form (not, of course, similar in actual detail or 

 density) are : — 



Agrionoptei'a, Macromia, Ictinuii, Anax, Gynacantha, the 

 group comprising the closely allied Australian genera of the legion 

 Frotoneura, Pse'udagrioii, Argioc7iemis, Ayriocnemh. Austro- 

 lesies, as an offshoot of the cosmopolitan Lestes, still very little 

 differentiated from the parent stock, exhibits, in Australia, a 

 very interesting contour intermediate between typical ectogenic 

 and entogenic form. It is, in fact, just in process of being 

 " budded " or separated off from the parent stock. 



A certain amount of evidence goes to show that small invasions 

 from the Oriental region have reached Australia by way of Timor. 

 My records are not, however, complete enough to present a con- 

 tour of this type for any group of Odo7iata, though I have little 

 doubt that such could be established as a result of careful collect- 

 ing in the North- West. 



We see, therefore, the probability of two distinct kinds of 

 ectogenic contour in Australia. For these I propose the names 

 Torresian and Timorean respectively, indicating the respective 

 paths by which the stream of immigration reached Australia. 



B. Eritogenic Contours. —Transparency 2 exhibits the contour 

 of the group Syjithemina, comprising the closely allied genera 

 Synthemia, MetatJiemis, and Choristhemis. This group belongs 

 to the subfamily Corduliimv, and has no near allies. The 

 contour shown is typical of the greater portion of the essentially 

 Australian fauna. It consists of two separate portions in which 

 the species are more or less differentiated from one another. A 

 large area is occupied on the east, extending from New Guinea 

 to Tasmania, while on the west the genus reappears in the 

 south-western corner of Australia. The separation of the two 



