JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The American Society of Parasitologists is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Parasitology. Michigan, Iowa, Alabama, Mississippi, Minnesota, and the District of Columbia from the hosts Sylvilagus floridanus, Lepus americanus, and Vulpes fulva (Doss et al., 1966, Index-Catalogue Med. and Vet. Zool., Trematoda and Trematode Dis. 5: 838) and from S. floridanus in Kansas (Franklin et al., 1966, Bull. Wildl. Dis. As. 2: 52-53). Measurements of 15 specimens of H. tricolor from S. transitionalis are given below. All measurements are in microns, with the first figure the mean, followed by the range in parentheses. Length 784 (683 to 887); width 483 (388 to 571); oral sucker 67 (61 to 82); acetabulum 65 (59 to 73); center of acetabulum to anterior end of body 202 (156 to 245); center of acetabulum to anterior end of body as per cent of body length 25% (22 to 31). These measurements were compared with measurements from Hasstilesia texensis Chandler, 1929, obtained from the small intestine of the marsh rabbit, Sylvilagus palustris, collected May 1961 in Dania, Broward County, Florida (new locality record), and with published measurements of H. texensis. Measurements of my material show H. tricolor to have a more anterior acetabulum and smaller suckers and pharynx than H. texensis. I agree in retaining the two species with Robinson (1959, Tr. Am. Micr. Soc. 78: 317-322) and with Lumsden and Zischke (1961, Tul. Stud. Zool. 9: 77-85), who used the same characters to separate the species. The synonymy of H. tricolor and H. texensis suggested by Marker and Cheng (1960, Michigan, Iowa, Alabama, Mississippi, Minnesota, and the District of Columbia from the