president's address. 661 



complete or almost complete absence of representatives of orders 

 which are abundant in other parts of the continent. This state 

 of things is sufficiently accounted for by the arid nature of the 

 countr}' and its unsuitability for their maintenance, or b}'- the 

 eiFectual climatic barrier which keeps them out. Thus, it would 

 seem that with the want of suitable perennial rivers and creeks 

 may be correlated the absence of Platj^pus, just as the absence of 

 forests accords with a dearth of arboreal Phalangers. Land 

 Planarians, Peripatus, Terrestrial Amphipods and Isopods, and 

 Slugs are among the other notable absentees (as well as Myrio- 

 pods — possibly an unintentional omission). 



Earthworms are poorly represented, only one species having 

 been found. This — a species of Acanthodrilus — is a treasure 

 which in quality compensates :^or some of the deficiency in 

 quantity. It is a good instance of discontinuous distribution, 

 and furnishes Professor Spencer with an opening for some 

 interesting speculations. The genus is one which in Australia 

 has lost ground, being at present but feebly represented in a few 

 widely separated localities. Formerly when the rainfall was 

 greater it was probably the dominant genus in the northern 

 portion of the Continent, as it still is in New Zealand and 

 elsewhere in the Southern Hemisphere. 



Butterflies and Lepidoptera generally are not numerously 

 represented. But the collection was made during the winter 

 months, or rather during a dry spell, which will perhaps to 

 some extent account for the scarcity. 



The positive characters are shown chiefly in this — that the 

 Larapintine fauna is a select assemblage of species which may 

 perhaps be roughly classified as very hardy species, and as species 

 which in habit or in structure have become specially adapted to 

 live in an arid region, or which have been able to take advantage 

 of some favourable external circumstances. 



Some of them doubtless are the lineal descendants of forms 

 which have uninterruptedly inhabited the region from a time 

 antecedent to the setting in of the Dry Period, which proved so 

 disastrous a change to forms like the Diprotodon. Others are 



