Abstract
Oncholaimus jessicae n.sp. is described from several sites in the Blyde River system in the eastern Transvaal. The new species closely resembles O. deconincki Heyns & Coomans, 1977, from which it differs mainly in the absence of males and details of the demanian system: the ductus entericus is much longer, the uvette is situated closer to the anus, and the main duct is better developed and glandular.