On a collection of Land-, Freshwater- and Marine Mollusca from Northern New Guinea

INTRODUCTION. The Mollusca, recorded in this paper, have been collected by Dr. P. N. VAN KAMPEN and Mr. K. GJELLERUP, during their abode in New Guinea, in 1910 and 1911. The collection is made near the eastern boundary of the Dutch part of the island. „Hollandia" is the name of a camp on the Kajo-bay, a small bay on the western coast of the Humboldtbay, „Hussin" a camp on the Bewani-river, „Zoutbron" (3° 1' 13" s., 140° 57' 30" e.) a camp on the Begouxe-river. The Mbai and Faté are small rivers, which flow in the Humboldtbay near Hollandia, the Tjahé is a small branch of the Mosso. The other localities are to be found on the map which belongs to an article of Capt. Sachse in the „Tijdschrift v. h. Kon. Nederl. Aardrijksk. Gen." (2), dl. XXIX, 1912, p. 36. The collection contains about 60 species, amongst which 9 are new to science; moreover a few new varieties have been described. Perhaps this number of novelties would have been still more considerable, if some of the difficult forms, such as Helicarion, had been at hand in larger number of specimens; but I did not like to encumber science with vague descriptions of new species, which could not be recognized by later students. I have to thank Mr. PH. DAUTZENBERG and Mr. G. K. GUDE, for their assistance in identifying some species, which were doubtful to me, and again Mr. J. J. VERWIJNEN for the loan of books from TEYLER'S Museum at Haarlem. I. LAND- AND FRESHWATER-MOLLUSCA. Class Gastropoda.