The last day of my stay in Pulo Panaitan (Prinsen Island), Str. of Sunda, I embarked on the M.V. „Alkai” with Mr. A. HOOGERWERF, the leader, and some other members of our expedition to make a last trip along the coast looking for a suitable place to set up a new bivouac. We tried in vain to come ashore at Legon Lentah and then went further South. Late in the afternoon we tried again to come ashore in Legon Lentah and this time we succeeded. Behind the sandy beach of hardly one meter in width I entered a Lumnitzera forest. In the dry season, when we saw this place, the sea does not cover this forest, a low ridge of sand and coral debris forming a wall bordering the forest on the seaward side. I venture to say, that in the rainy season, except at spring tides and storms, the seawater will not cover this forest either, although the salty groundwater will rise. A large swamp will then be formed by considerable quantities of fresh water coming down the hills. This brackishwater basin will for a fairly long period contain stagnant water. I noted that the vegetation at this point consisted of Lumnitzera racemosa and here and there a Sonneratia alba of which the pointed roots peaked upward through the surface. Further inland the vegetation changed and trees with bent stilt roots (Rhizophora mucronata) dominated. At the sea-side the ground was very muddy, further inland somewhat drier, higher and stony. In this area I collected Planorbis convexiusculus, Thiara tomatella, Thiara tuberculata and Neritina variegata, all dead. The living molluscs in this area were Polymesoda expansa, and Telescopium telescopium. The bivalves alive, with their shells closed, were found in the mud for about half their length or more, the gastropods close together in groups of four to six, the apertures pressed into the mud as were the ventral sides of their shells, the apices pointing outward, the apertures to the centre. The party returned, none of the members having found fresh water. Finding the Planorbis and Thiara shells, I thought that fresh water might be present in the bottom, but when Mr HOOGERWERF tasted the water after having dug for it, he found it salt. The salt water was about 50 cm below the surface. Then, at the moment that the launch was about to return to the Alkai, I found Telescopium shells differing very much from Telescopium telescopium. These specimens behaved in the same way as T. telescopium, grouping together, apertures in the centre, pressed into the mud, the apices pointing outwards. I had time to collect only five of the aberrant Telescopium shells and walking back to the launch I noted that T. telescopium was living in the seaward part of the area, while the other Telescopium were living more inland on slightly higher and somewhat stony ground, where Lumnitzera and Sonneratia gave way to the bent stilt roots of Rhizophora mucronata. We arrived in our bivouac after sunset. My luggage had been packed already. On reaching home (October 1st) I was able to look after my shells. The animals were already decomposing.