During a night in August 1910 Mr. P. Buitendijk catched on the road of Panaroekan, with the pelagic net, a curious Heteronereis-specimen, differing from the species usually met with by the shape of its cephalic lobe, but agreeing in many regards with a similar form from the Gulf of California, collected in 1900 by Diguet and afterwards described by Gravier ¹). Our worm (a ♂) is rather small, measuring only 13 mm. in length, whereas the largest of the California-specimens reaches 23 mm.; the number of its segments amounts to 95. The body shows dorsally on each side a double row of black spots, consisting of a narrow transverse one at the base of each foot and another round patch on the middle of it; veutrally also there occurs a dark spot at the base of each foot. On the other hand the California-species is characterized by a dark transverse band about across the middle of the dorsum of each segment. The prostomium (figs. 1 and 2) is broadly rounded anteriorly, somewhat resembling the bill of a duck, with a longitudinal ridge along its middle. The two pairs of eyes are highly enlarged, close to each other. However only the posterior pair, globular in shape, is situated dorsally, with the lens directed upwards; the anterior pair, elliptical in shape, is for the greater part situated ventrally, having its lens directed downwards. As suggested by Gravier, these pelagic worms probably are swimming as easily on their back as on their belly.