Two species belonging to the Nematode genus Physaloptera have up to the present been reported from Man; P. caucasica v. Linstow, 1902, which has been obtained on one occasion only from the Caucasus, and P. mordens Leiper, 1908, which has been reported on several occasions from Man and Monkeys from Central Africa. Until quite recently the only account of the former species was that of v. Linstow, and from this it was quite plain that the two species were distinct. Schulz (1926), however, has had the opportunity of re-examining the types of P. caucasica and on the basis of his excellent descriptions and figures it is possible to make a closer comparison between it and P. mordens. Schulz was able to rectify several inaccuracies in v. Linstow's description, and he came to the conclusion that the two species were very closely related, the only difference between the two being that in P. caucasica there is in addition to the three large teeth on each lip also a series of small teeth between and exterior to them on the inner face of the lip, which teeth are absent in P. mordens; also that the former species was smaller than the latter, 14–24 mm. to 29–34 mm. for the male and 24 mm. to 41–100 mm. for the female respectively, and that the eggs of the former were larger.