SLADEN TRUST EXPEDITION TO ABROLHOS ISLANDS. 127 



THE PERCY SLADEN TRUST EXPEDITIONS TO THE ABROLHOS 

 ISLANDS (Indian Ocean). 



Under the Leadership of Prof. W. J. Dakin, F.L.S., F.Z.S. 



Report I. — Introduction, General description of the Coral Islands forming 

 the Houtman Abrolhos Group, the Formation of the Islands. By W. J. 

 Dakin, D.Sc, F.L.S., Professor of Biology, University. of West Australia. 



(Plates 10-14, and 12 Text-figures.) 

 [Read 1st February, 1917.] 



INTRODUCTION. 



Shortly after my arrival in Western Australia in 1913 my attention was 

 drawn to the interesting position of certain coral islands known as the 

 Houtman's Abrolhos Islands. I determined to visit the group at the earliest 

 possible date, and to this end applied to the Trustees of the Percy Sladen 

 Trust for a grant in aid. An expedition was planned and left the Australian 

 Coast in November 1913 for the islands. On this occasion I was fortunate 

 in having a very able colleague in Mr. W. B. Alexander, M.A., of the West 

 Australian Museum, and the grant of the Percy Sladen Trustees was 

 supplemented by aid from the University of West Australia and the West 

 Australian Museum. Part of our equipment was conveyed direct to the 

 islands from Fremantle, but the personnel with the rest of our apparatus 

 and stores, etc., travelled by train to the port of Geraldton, where the fishing 

 lugger ' Queen/ a boat of 22 tons, awaited us. The 'Queen'' is one of a fleet 

 of fishing-boats which makes Geraldton its headquarters, and fishes the waters 

 round the Abrolhos Islands, and as far north as Shark's Bay. 



Geraldton is a port of about 3500 inhabitants, situated on the coast of 

 Western Australia in latitude 28° 46' S. Although only a small town it 

 ranks as the second or third port in Western Australia, and is the centre for 

 a large agricultural and pastoral area, as well as the Murchison goldfield. It- 

 marks the most northerly point on (he coast which can be reached by train 

 from Perth, and it will be seen on reference to a map that a great length of 

 the coastline of Western Australia remains to the North and can only be 

 visited with difficulty. There are a few ports which are reached by regular 

 steamers from Perth, but between these places the coast might almost still 

 be termed unexplored ; this certainly holds good, from the biological point of 

 view, for the entire coast north of Geraldton with the exception of Shark's Bay. 



The Abrolhos Expedition of 1913 extended over a period of three weeks, 

 during which time we worked the ' Queen ' from islet to islet, and 

 combined shore collecting with biological and geological observations on 

 the islands, and some dredging in the lagoons and between the island 



LINN. JOURN. — ZOOLOGY, VOL. XXXIV, . 10 



