22 
It would appear that the islands now forming the Wallaby 
Group were once joined up and the coral mass was much more ex- 
tensive than at present. The present condition is the result of sub- 
sidence and erosion followed by a more recent small uplift and then 
further erosion. There is considerable evidence for this small recent 
uplift, the extent of which is about eight feet. In fact, many of the 
small islands are probably only islands at present owing to this 
elevation. They had previously been cut down to sea level. One is 
tempted at first to assume that the Abrolhos are coral islets of past 
times and that the conditions which brought them into being are non- 
existent now at this place. I think, however, that on second thought 
this view will be dismissed. The Pelsart Group would hardly have 
retained its atoll-like structure unless the conditions favouring the 
growth of reef-building corals were very recently prevailing. More- 
over, in suitable places in the lagoons one finds great masses of 
living corals, two species of Madrepora with very different growth 
habits being most abundant. No single theory of coral island 
formation is going to expain the various coral formations of our 
tropical seas. Every coral island or group of islets needs separate 
examination before its mode of origin can be explained, and the 
Abrolhos Islands offer problems for almost every branch of oceano- 
graphic research. 
Notes on some animal groups, chiefly marine. 
The following brief notes contain several new records made 
during the past fourteen months. In many cases it is impossible for 
us to determine species owing to the absence of literature. It may 
be of some little value to refer to the genera, especially as they are 
in certain cases first records of their Phyla or Sub-Phyla from the 
West Australian Coast. 
Sponges. — Very little systematic work has been carried out on 
our sponge fauna up to date. The coast appears, however, to be 
particularly rich in sponge species. Two reports of the Hamburg 
Expedition collections refer only to the Tetraxonida of the South- 
West. At the present time Professor Dendy has our collection 
from the Abrolhos for the purpose of investigation. Most of the 
specimens of the Tetraxonida collected by Michaelsen and Hartmeyer 
were quite new to science. 
Coelenterata. — We possess very little knowledge of the 
Coelenterata of Western Australia. Two papers have so far ap- 
peared on the specimens collected by the German expedition — one 
on the Actiniaria and another on certain Aleyonaria. Many of our 
corals have been named, but a revision of this work is badly needed. 
Although reef -building corals are stated not to occur south of Sharks 
Bay, except at the Abrolhos, some species of corals may be obtained 
k, 
