On two earlier occasions I had the privilege to describe new species of landsnails collected by Mrs. G. A. TAMMES-BOLT in Celebes ¹). This time it is a member of the genus Opisthostoma which I want to introduce. The genus belongs to the operculate landshells, family Cyclophoridae, and occurs in India, Tonkin, Siam, Malaya, Borneo and Java. The record in Celebes is new and adds a new territory to its distribution. On the whole some 40 species have been described, some of them famous for their eccentric shape, and all of small, or very small size, the maximum dimension not surpassing 5 mm. and generally even less.