On our return to Tremouille Island Mr. Fitzmaurice joined us, having completed the examination of the Montebello Group, a large proportion of chart material, in a very short space of time, considering the number of small islands, which would render it an endless labour to attempt any description, further than that they lie something in the shape of a scythe. RITCHIE'S REEF. A hill 145 feet high, the loftiest point of the group, rises near the centre of Tremouille, the north-east island, off the north-west end of which a ledge extends in the direction of an out-lying reef, bearing North 55 degrees West (magnetic) nine miles and a half, which places it in latitude 20 degrees 17 minutes South and longitude 0 degrees 26 minutes West of Swan River; or 115 degrees 21 minutes East. This could be no other than that which we had so often looked for as Ritchie's Reef, as our former tracks to the westward had assured us that it did not lie in that direction. In latitude it agreed with the position given to it on the charts, but in longitude it differed considerably, lying full half a degree to the eastward. It therefore appeared not to be a discovery of Lieutenant Ritchie's, as it had been not only seen previously by the French, who had considered it as a reef extending off Tremouille Island, but many years before by Captain Clerke, who placed it in latitude 20 degrees 18 minutes South, nine or ten miles North-West (magnetic) from what he thought to be Rosemary Island, but which it is very evident was Tremouille. The name then of Clerke's Reef should be given it instead of Ritchie's. WALLABY SHOOTING. Mr. Fitzmaurice having seen plenty of wallaby on the larger islands, a party of us went on shore in the evening, after securing observations for the rates of the chronometers on a small islet called Flag Islet, near the centre of the rocky cluster fronting the eastern side of Hermite Island. This can be recognised by it alone having a sandy point on the south-west end, which we placed in latitude 20 degrees 27 minutes 47 seconds South and longitude 0 degrees 8 minutes 20 seconds west of Swan River. The time of high-water here at full and change, was about 10 o'clock, when the tide rose fourteen feet; the flood-stream came from the northward.