It is well known that the genus Trachycystis is mainly centred in South Africa, but several species have been described from East Africa. The proper generic grouping of these northern species is not really certain since no examination was made of the animals. Also some of the species referred to Goniodiscus, Pyramidula and even very diverse genera may in truth be, in fact almost certainly are Trachycystis species. T. ambigua Conn., a member of the subgenus Psichion, is known from Portuguese East Africa and the writer has given an account (VERDCOURT, 1952, p. 62) of a specimen from the East Usambara Mts., (Amani) N.E. Tanganyika which seems to be this species and agrees in every way with the description.¹) The subgenus has the most characteristic radula, which is different from any other genus and utterly unmistakable. A further member of the subgenus was found crawling on the leaves of Acokanthera in the Karura forest near Nairobi, Kenya (Amani specimen was also on a bush) ²).