Reptiles collected in the vicinity of the Iowa Lakeside Laboratory, Dickinson County, Iowa, during the summer of 1950, were examined for helminths by Burnham (1951) and for protozoa by Schmidt (1954). lvlonocercomonas colubrorum, Trichomonas batrachorum and Haemogregarina sp. were found in both Thamnophis radix and T. ordinatus parietalis. An enteric flagellate of the genus Trimitus was found in a single specimen of T. radix. Special consideration is herein given to Trimitus because though this genus has been reported from North American amphibians and reptiles it appears that neither descriptions nor figures have been published, and also, because there is some uncertainty concerning the characterization of the genus