HOUTMAN ABROLHOS ISLANDS. 153 



surface of which is limestone. No sand or guano hides the rock in this area 

 now, but a few bushes are rooted in the crevices and cracks in the weathered 

 limestone surface. This flat area occupies the greater part of East Wallaby 

 Island, and s:ind-hills are not met with again until one reaches the extreme 

 west and northern coasts. It might be expected that the flat area we have 

 described with the coral-limestone surface would be as many feet above sea- 

 level as the highest limestone exposed on the East coast. This is not the case, 

 it is only about 10 feet above sea-level. It is only on the East coast of East 

 Wallaby Island that any limestone higher than this is found. At the same 

 time, the land rises once more on the western margin, so that the greatest 

 heights are found on the East and West coasts. If, however, the eastern 

 elevations are examined, they will be found to be composed entirely of sand, 

 and the exposures are quite interesting. One of these eastern sand-hills is 

 marked on the chart with an elevation of 35 feet — a well is indicated about 

 200 yards to the N.E. of it. Now just north of this saud-hill the wind has 

 cut an extraordinary pass right through the hills and eroded it down to the 

 limestone surface. The sides of the pass are perfectly vertical and there is 

 abundant evidence that the whole is due to the wind. It is quite obvious 

 here that the high land is due chiefly to blown sand. 



The southern extremity of East Wallaby Island towards the channel is 

 the lowest part of the island, and a sand-beach presents a marked contrast 

 to the cliffs of the eastern shore. This sandy beach extends up the western 

 shore to the north-western corner of the island where cliffs again appear, 

 but only 3-4 feet in height and have a sandy beach at their base. The 

 northern beaches are also of sand, with sand-hills behind, until Fish Point is 

 reached on the east of Turtle Buy. Samples of the shore-sand from the 

 north and west beaches of East Wallaby Island have been examined. The 

 sand consists almost entirely of calcareous matter : — foraminifera, shell- 

 fragments, coral particles, and echinoid spines. The foraminifera are all 

 shallow-water forms, the predominant genera being Orbitolites, Polystomella, 

 and Peneroplis. Other common forms are species of Miliolina, Planorbulina, 

 Glohigerina, and Pulvinulina. 



A reef-flat exists all round the island, but it presents some points of 

 difference on the various coasts. On the east coast (Recruit Bay), it is 

 narrow, 100-200 feet or so in width, and extends to the base of the lime- 

 stone cliff. It is covered with living Vermetus, and broken up with irregular 

 hollows every here and there. To the south it forms a great expanse con- 

 necting East Wallaby Island with West Wallaby Island. On the west of 

 the island the reef-flat is wider and extends out for at least a quarter of a 

 mile from the beach, which, as we have already noted, is of sand. The same 

 aspect presents itself again on the north-west, and there is much sand and 

 weed growths here. A considerable quantity of decaying weed is conspicuous 

 on the eastern and northern shores. 



