Abstract
This paper describes the new species Mallomonas papuensis from a small bog pool in Papua province, Indonesia. The description is based on silica-scale morphology studied by means of transmission and scanning electron microscopy. The cells of Mallomonas papuensis are covered by three types of scales: asymmetric collar scales with forward projecting spines, rhombic body scales and oval posterior scales with short spines. The shield of all scales types lacks ornamentation. We were not able to find any specimens with bristles or isolated bristles although the small dome is visible on the collar scales. Mallomonas papuensis belongs to the section Torquatae and closely resembles M. newfoundlandicus. Distinctions from other similar taxa are discussed.