On a remarquable fresh-water Polychaete "Nereis nouhuysi" from the East-Indies

In the year 1905 Mr. J. W. van Nouhuys presented to our Museum some Nereis-specimens, collected in the Miha at the South-coast of the isle of Taliaboe, at a distance of two hours from the mouth of the river, that moreover was shut off by a bank of gravel 1). There are eleven specimens, ten females and one male, all mature and in the Heteronereisform. They are characteristically marked; in the median body-region each segment shows on it dorsal side a transverse, black band, narrow in the piddle and growing broader laterally, on the base of the parapodia. Two black spots occur on the dorsal side of each parapodium, whereas the dorsal ligule is also black coloured. Ventrally the segments show a similar marking; however on the base of the parapodium there occurs an oval spot, consisting of longitudinal lines and in front of it a small transverse patch. The anterior ten or twelve segments have a dark brown hue, with pale, oblique stripes on their lateral part; the head also is dark coloured, its posterior part being somewhat paler. The largest specimen has a length of 110 mm. and consists of 225 segments. The head is longer than broad, elongated trapezoidal; its antennae are small, whereas the palps are stout, with a small distal joint. The eyes are large and nearly coalesce. The longest tentacular cirrus extends to the eight segment. The armature of the proboscis consists on area I or a transverse, indistinctly tristichous group of about 13 to 18, distant, hook-shaped paragnaths; on areas II and IV there occurs a curved, distichous or tristichous group of acute, hook-shaped paragnaths; area III has a broad group of 45 to 50 paragnaths, arranged in 5 or 6 rows, the lateral ones being