Trachygystis (Dendrotrichia) sylvicola, a new subgenus and species from Rhodesia (Mollusca, Gastropoda Pulmonata: Endodontidae)

In 1959 the first author (A.C.v.B.) discovered a peculiar snail of the pulmonate family Endodontidae in Rhodesia; on a subsequent expedition more specimens were obtained, so that a series is now available for description. The species undoubtedly belongs to the genus Trachycystis Pilsbry, 1893, but a new subgenus has to be created in order to accomodate this particular species. Anatomical data and figures have been supplied by the second author (B.V.), while the first author is responsible for the remaining part of text and figures. Dendrotrichia subgen. nov. A subgenus of Trachycystis characterised by ramose bristles on the surface of the shell; genital anatomy like that of subgenus Chalcocystis. Type species: Trachycystis (Dendrotrichia) sylvicola spec. nov. Trachycystis (Dendrotrichia) sylvicola spec. nov. Shell (pl. 1) small, depressed subconic, umbilicate, thin, somewhat transparent, dull, hirsute, corneous. Spire depressed, apex mamillate. Whorls 4-41/2, regularly increasing, nearly flat, bluntly shouldered at periphery, first 11/2 smooth, remainder covered all over with sharp, curved, oblique, transverse costae, increasing in strength on each succeeding whorl, the interstices filled with microscopic transverse striolae, increasing in number with the widening of the interstices, cut by close, strong, regular spiral lines; basal sculpture similar though somewhat weaker, the ribs converging into the umbilicus. All costae bear long (up to 1.2 mm), stiff, ramose, bristles (fig. 1) at regular intervals, usually more or less at right angles with the shell; the bristles consequently form spiral rows, of which there are 6 or 7 on the body whorl. The bristles are longest and most closely packed on the