A new species of Pseudobba (Mollusca Gastropoda) from western New Guinea

Pseudobba boschmai nov. spec. Description. — The shell is large, very globose, umbilicate, and more or less irregularly obliquely ribbed; it is peculiarly striate-pitted between the ribs. The apex is obtuse. The whorls number 6 1/2, the upper are slightly convex, the following soon become more convex, while the ultimate whorl is very large, convex, and descending in front; the sutures are impressed. The upper whorls are dark fawn-coloured, gradually becoming darker; the body whorl is of a beautiful chestnut colour, becoming blackish towards the aperture, this colour is visible as a vertical band of about 1 cm broad; it does not obtect the reflexed peristome which is white and has a white lip. The aperture is dark and smooth. The peristome is nearly circular, its upper margin is narrow and straight, its basal margin is broader and passes abruptly into a large triangular to subquadrate plate, which is shining white and curves inwards, spirally encircling the axis of the shell. The two extremities of the peristome are united by a curved shallow impression; the base of the peristome is convex and descends regularly into the deep cylindrical umbilicus, which is about 3 mm wide, and which is not obtected by the columellar plate. Laterally the peristome is provided with a characteristic funnel-shaped white spot, which more or less distinctly surrounds the umbilicus. The height of the holotype is 40.6 mm, its greatest diameter is 42.5 mm. Material examined. — Six specimens were collected about halfway between the mouth of the Mamberamo River and Hollandia (now Kota Baroe), north of the Sidoearsi Mountains between the villages Abentie and Kondirdjan, Western New Guinea (17 June 1959, leg. F. A. W. Schram).