HOUTMAN ABROLHOS ISLANDS. 171 



extremely common. We could have obtained hundreds o£ specimens of 

 Aphjsia by merely picking them up as we waded in the shallow water. 

 Under the larger coral blocks was a rich ascidian and sponge fauna, and one 

 or two cidarids were obtained. Alpheids and other Macrura abound. 



Reference must be made also to our dredge hauls. We dredged in 

 the lagoon, but obtained little except on certain patches where we procured 

 several species of Ascidians (simple and compound) not met with elsewhere, 

 and some coral blocks with Brachiopods adhering to them. Against the 

 edge of the reef -flat (lagoon) we obtained little else but fragments of rotten 

 coral, and, as already pointed out, further north we obtained coral mud and 

 nothing else. 



In the passage south of Wooded Island the dredge brought up great 

 quantities of weed. We have already referred to the algse as being common 

 at other places. Asa matter of fact, it appears strange to the writer to 

 find so much coral growth and a rich algal flora in close proximity. 

 Unfortunately I have not yet been able to see a coral reef in real tropical 

 waters — the comparison with the Abrolhos would be interesting in many 

 respects. On our last expedition to the Abrolhos we made a good collection 

 of these algce and they now await examination. 



THE PELSART GROUP. 



We have emphasized the fact that the Abrolhos Islands are extremely far 

 south for a rich growth of reefs. It is interesting to note that it is the 

 Pelsart Group — the most southern group of the Abrolhos Islets — which 

 most resembles an atoll, and which has given us our best collecting. It is 

 also the historically interesting region of the Abrolhos. 



The Pelsart " Group " consists of a more or less triangular lagoon 

 bounded on two sides by a continuous coral reef, and more or less open to the 

 sea on the north. There are three small islets in the lagoon — Gun Island, 

 Middle Island, and Square Island — together with some smaller islets not all 

 properly charted. Deep water is found closer to the encircling reef than 

 to the outer islets of any of the other Abrolhos Groups, and, on the ocean 

 side, depths of over 100 fathoms are quite near, whilst even on the eastern 

 side the depths are at least two or throe fathoms greater than to the east of 

 the more northerly islets. 



The Western margin of the Pelsart Atoll is formed of a lono- reef 

 extending for upwards of 14 miles without any breaks, and without any 

 heaping of coral fragments above high-tide level to form islets. This reef 

 rises about one foot so above low-water mark. 



On the Eastern side of the Pelsart Lagoon there is a typical rim islet — 

 Pelsart Island. This is the longest in the Abrolhos Group and extends for 

 about eight miles. It is quite narrow, being in some places only a few 

 hundred feet across. At the extreme southern end of Pelsart Island (which 



