During the past few months the writer has been able to examine an unusually large series of male and female nematodes of the genus Rictularia from the eastern half of the United States. About half of these were specimens from rodents and bats in the collection of Dr. Robert Rausch. Ten bottles of rodent material were loaned from the U. S. National Museum Helminthological Collection by Dr. E. W. Price. Dr. Reinard Harkema contributed the material collected from Peromyscus leucopus leucopus and reported by himself (Harkema, 1936). Dr. J. A. McLeod courteously loaned his type specimens of R. citelli. Mr. L. Wayne Wilson loaned one of the specimens which he reported from Peromyscus leucopus noveboracensis (Wilson, 1945). Thanks are expressed to Dr. L. J. Thomas for helpful suggestions relative to preparing the drawings for publication. As' the status of several species of North American Rictularia has been rather confused, it is hoped that the observations which follow will prove themselves essentially correct: that they will be of some value to future workers who happen to have an opportunity to examine more material.