Notes on species of the genus Amphidromus (Mollusca, Pulmonata, Pleurodontidae) from Islands Lying off the coast of Sumatra, with descriptions of new races based on collections made by Dr. E. Jacobson in 1913

Dr. E. Jacobson spent some months on the island of Simalur, and on some of the smaller islands in its immediate neighbourhood in the course of the year 1913. He made extensive zoological collections on these islands, whose fauna was very little known up till that time. Amongst his material was a series of shells belonging to the Pleurodontid genus Amphidromus. This series has been entrusted to me by Dr. Van Regieren Altena, and I am grateful to him for the chance of seeing these very interesting shells, and for the help he has given me in dealing with them. I have too to thank Mr. G. L. Wilkins for the figures. Simalur is the most northerly of the long chain of large islands which lie along the West coast of Sumatra. The whole chain is roughly 1000 km in length from North to South. Its several islands are separated from Sumatra, and to some extent from each other by sea-depths of 500-1000 fathoms. Simalur itself is about 90 km in length; Pulau Babi or Saranbau is a smaller island lying S.E. of Simalur. Oelau Lekon (or Lekoeen) is a still smaller island near Pulau Babi. Dr. Van Regieren Altena tells me that Oelau is a local form of the Malay word Pulau. Loosjes (1953) has described Pseudonenia Jacob soni, a Clausiliid, collected by Dr. Jacobson on Simalur. Apart from this I can find no record of land mollusca from the island. On the other hand three species of Amphidromus have been recorded from Nias Is. which lies about 100 km South of Simalur and is rather bigger. These species were described by Fulton (1907), and a full account of the land molluscan fauna of Nias was published by Van Benthem Jutting (1934-193S).