During the course of my investigation of the parasitic infection of various fishes of the Calcutta markets, I came across a new acanthocephalan parasite, Neoechinorhynchus topseyi, from the intestine of Polynemus heptadactylus, commonly known in Bengal as Topsey or mango-fish. The host was available in the local market during the months of February-August, and infection with this parasite marked during May-July. A single case was, however, noticed in August 1935 when after the intestine was taken out a portion of the threadlike parasite was seen hanging from its anal region. The intestine was slit open and it was found that one gravid female measuring 69 × 1· mm. was the only occupant of the entire lumen of the gut. The parasite was attached by means of its proboscis to the anterior part of the intestine near the duodenum.