Acanthodrilus ere mi us, a Neio Species of EarfJucorm. 
By BALDWIN SPENCER, M.A., 
Professor of Biology in the University of Melbourne. 
(Plate 29). 
The arid nature of the country and the fact that only very rarely is black 
soil met with in Central Australia made it very unlikely that many earthworms 
would be found. I had, however, no idea that the earthworm fauna would be of 
such a meagre description, as previous experience in Victoria, Tasmania and 
Queensland had shown me that earthworms were to be found in the most unlikely 
spots, and as a constant search was made I do not think it likely that available 
forms were overlooked. At the same time it is quite possible that moi’e than the 
single species which we found does exist, but to secure them you probably need to 
be on the spot immediately after the fall of rain. 
During the course of our Expedition it was only on three occasions that very 
limited patches of damp black earth were met with, once by the side of a water- 
hole in the James Range, at Illamurta, once in the George Gill Range, and once 
in the McDonnell Range on the Finke River. 
Though these spots are separated by wide tracts of country quite impassable 
to earthworms, yet in each one there is found only the single species which is 
referable to the genus Acanthodrilus. 
It has already been pointed out by myself in the case of mammals, and by 
Professor Tate in the case of molluscs, what a vast influence the change from a 
pluvial to a desiccating climate has had upon the early fauna of the central area. 
The majority of the forms became extinct, whilst a certain number wei’e preserved 
in sheltered and favourable spots. 
Now there can be little doubt but that the earthworm is not a recent 
introduction : not even the widespreading Allolobophora introduced from Europe 
has yet made its way into the interior, nor is there any trace of any of the 
dominant Australian genera, such as Megascolides or Cryptodrilus. If such 
abundant forms have not been introduced, it is scarcely likely that the rarest 
genus in Australia should have been carried to three spots separated from one 
