Two new species of the genus Trachycystis from South Africa (Mollusca, Gastropoda Pulmonata, Endodontidae)

The genus Trachycystis Pilsbry, 1893, is represented by more than a hundred species in southern Africa. It belongs to the family Endodontidae, which is one of the six dominant families of terrestrial molluscs in South Africa (Van Bruggen, 1978). The large number of species as well as the fact that many of them have not been well described, makes this an extremely difficult genus to deal with taxonomically. The matter is complicated further, especially for local workers, because most of the type specimens are dispersed in European museums. Since 1974 the author has been engaged in a study of the terrestrial molluscs, found at the top end of a narrow cliff, called Landdroskloof, situated on the western slopes of the Hottentots Holland mountains, 34°02' S 18°59'E. The locality falls in the recently proclaimed Hottentots Holland Nature Reserve and is about 60 km east of Cape Town and 1350 m above sea-level. The Jonkersnek rain gauge which is only about 5 km away from this site, is known to have recorded a 15-year (1945-1960) mean annual rainfall of 3539.2 mm. This is the highest measured mean precipitation in South Africa. Specimens were collected during different seasons of the year. Among the several interesting molluscs species which inhabit this area, two yet undescribed species of the genus Trachycystis were found. As the habitat varies considerably in such a mountainous region, it can be expected that stenotopic species would only ocur in certain limited microhabitats. The two new species live in places which are sheltered from the sun for at least a few hours per day. The vegetation in these places consists of a thick growth of Cyperaceae and Restionaceae, among others Restio perplexum. These con-