770 STUDY OF THE ODONATA OF TASMANIA, 



along the north-western line. These have not added any new 

 species to the list. 



An examination of the material in the Hobart Museum enabled 

 me to add further localities to my list, and also to note the occur- 

 rence of a new species in the Hobart district. The total number of 

 species, therefore, now stands at twenty. 



Though it is probable that further careful collecting may result 

 in the addition of a few more species, yet the list, as it stands, must 

 be by now fairly complete. As it presents some very extraordinary 

 features which seem to me to offer very decisive evidence concern- 

 ing the nature and extent of the land-connection (Bassian Isth- 

 mus), known to have existed formerly between Tasmania and the 

 mainland, I have thought it advisable to put the facts on record. 



Two facts strike one, at once, as being very remarkable in the 

 case of the Tasmanian Odonata : — 



(1) Although the island is richly watered almost everywhere by 

 permanently running rivers, very few Odonata occur on them; 

 whereas the donate fauna of the lagoons and lakes is astonishing- 

 ly abundant. 



(2) Many of the very commonest species, to be found all over 

 Southern Victoria, are completely absent from Tasmania. 



It occurred to me that the nature and extent of the Bassian Isth- 

 mus must have played a very considerable part in this distribution. 

 If the Isthmus was, for a very long time, too broken or narrow to 

 possess any permanent running water, it would follow that only 

 those Odonata that were capable of breeding in stagnant water 

 (small lagoons, pools or waterholes), would be able to cross into 

 Tasmania, while all those species, whose larvae require running 

 water, would be shut out. I, therefore, made a list of the dragon- 

 flies of Southern Victoria (for which the records are very com- 

 plete) and divided them into two portions. 



A. — Those that have never been known to breed in still water. 



B. — Those that habitually breed in still water. 



This list comprises forty-two species, including all the known 

 Victorian Odonata except a few exceedingly rare species only re- 



